blktrace: Fix uaf in blk_trace access after removing by sysfs

blktrace: Fix uaf in blk_trace access after removing by sysfs

This is an automated ID intended to aid in discovery of potential security vulnerabilities. The actual impact and attack plausibility have not yet been proven.
This ID is fixed in Linux Kernel version v4.19.209 by commit 677e362ba807f3aafe6f405c07e0b37244da5222, it was introduced in version v2.6.30 by commit c71a896154119f4ca9e89d6078f5f63ad60ef199. For more details please see the references link.