xenbus: Use kref to track req lifetime

{
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "unaffected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "drivers/xen/xenbus/xenbus.h",
                        "drivers/xen/xenbus/xenbus_comms.c",
                        "drivers/xen/xenbus/xenbus_dev_frontend.c",
                        "drivers/xen/xenbus/xenbus_xs.c"
                    ],
                    "versions": [
                        {
                            "version": "fd8aa9095a95c02dcc35540a263267c29b8fda9d",
                            "lessThan": "0e94a246bb6d9538010b6c02d2b1d4717a97b2e5",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "fd8aa9095a95c02dcc35540a263267c29b8fda9d",
                            "lessThan": "f1bcac367bc95631afbb918348f30dec887d0e1b",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "fd8aa9095a95c02dcc35540a263267c29b8fda9d",
                            "lessThan": "4d260a5558df4650eb87bc41b2c9ac2d6b2ba447",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "fd8aa9095a95c02dcc35540a263267c29b8fda9d",
                            "lessThan": "8b02f85e84dc6f7c150cef40ddb69af5a25659e5",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "fd8aa9095a95c02dcc35540a263267c29b8fda9d",
                            "lessThan": "cbfaf46b88a4c01b64c4186cdccd766c19ae644c",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "fd8aa9095a95c02dcc35540a263267c29b8fda9d",
                            "lessThan": "8e9c8a0393b5f85f1820c565ab8105660f4e8f92",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "fd8aa9095a95c02dcc35540a263267c29b8fda9d",
                            "lessThan": "2466b0f66795c3c426cacc8998499f38031dbb59",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "fd8aa9095a95c02dcc35540a263267c29b8fda9d",
                            "lessThan": "1f0304dfd9d217c2f8b04a9ef4b3258a66eedd27",
                            "status": "affected",
                            "versionType": "git"
                        }
                    ]
                }

{
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "affected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "drivers/xen/xenbus/xenbus.h",
                        "drivers/xen/xenbus/xenbus_comms.c",
                        "drivers/xen/xenbus/xenbus_dev_frontend.c",
                        "drivers/xen/xenbus/xenbus_xs.c"
                    ],
                    "versions": [
                        {
                            "version": "4.11",
                            "status": "affected"
                        },
                        {
                            "version": "0",
                            "lessThan": "4.11",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "5.4.294",
                            "lessThanOrEqual": "5.4.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "5.10.238",
                            "lessThanOrEqual": "5.10.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "5.15.183",
                            "lessThanOrEqual": "5.15.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.1.139",
                            "lessThanOrEqual": "6.1.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.6.91",
                            "lessThanOrEqual": "6.6.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.12.29",
                            "lessThanOrEqual": "6.12.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.14.7",
                            "lessThanOrEqual": "6.14.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.15",
                            "lessThanOrEqual": "*",
                            "status": "unaffected",
                            "versionType": "original_commit_for_fix"
                        }
                    ]
                }