SUNRPC: close backchannel before destroying callback service

{
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "unaffected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "fs/nfs/callback.c",
                        "include/linux/sunrpc/bc_xprt.h",
                        "net/sunrpc/backchannel_rqst.c"
                    ],
                    "versions": [
                        {
                            "version": "441244d4273a8037b265fd254dfdaca5fa736ee2",
                            "lessThan": "6debde9e3e6ae21dcca75837b4247b13ca4ea2b8",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "441244d4273a8037b265fd254dfdaca5fa736ee2",
                            "lessThan": "3674f780f47d2906b5a0f7199b66973067bdfeca",
                            "status": "affected",
                            "versionType": "git"
                        }
                    ]
                }

{
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "affected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "fs/nfs/callback.c",
                        "include/linux/sunrpc/bc_xprt.h",
                        "net/sunrpc/backchannel_rqst.c"
                    ],
                    "versions": [
                        {
                            "version": "6.19",
                            "status": "affected"
                        },
                        {
                            "version": "0",
                            "lessThan": "6.19",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "7.2.4",
                            "lessThanOrEqual": "7.2.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "7.3",
                            "lessThanOrEqual": "*",
                            "status": "unaffected",
                            "versionType": "original_commit_for_fix"
                        }
                    ]
                }