fscache: delete fscache_cookie_lru_timer when fscache exits to avoid UAF

{
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "unaffected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "fs/netfs/fscache_main.c"
                    ],
                    "versions": [
                        {
                            "version": "12bb21a29c19aae50cfad4e2bb5c943108f34a7d",
                            "lessThan": "c1fc36d5470335546c45799d94d7bb2cbc09e8b7",
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                            "status": "affected",
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                        }
                    ]
                }

{
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "affected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "fs/netfs/fscache_main.c"
                    ],
                    "versions": [
                        {
                            "version": "5.17",
                            "status": "affected"
                        },
                        {
                            "version": "0",
                            "lessThan": "5.17",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.1.160",
                            "lessThanOrEqual": "6.1.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.6.51",
                            "lessThanOrEqual": "6.6.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.10.10",
                            "lessThanOrEqual": "6.10.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.11",
                            "lessThanOrEqual": "*",
                            "status": "unaffected",
                            "versionType": "original_commit_for_fix"
                        }
                    ]
                }