block: fix blktrace debugfs entries leakage

In the Linux kernel, the following vulnerability has been resolved:

block: fix blktrace debugfs entries leakage

Commit 99d055b4fd4b ("block: remove per-disk debugfs files in

blk_unregister_queue") moves blk_trace_shutdown() from

blk_release_queue() to blk_unregister_queue(), this is safe if blktrace

is created through sysfs, however, there is a regression in corner

case.

blktrace can still be enabled after del_gendisk() through ioctl if

the disk is opened before del_gendisk(), and if blktrace is not shutdown

through ioctl before closing the disk, debugfs entries will be leaked.

Fix this problem by shutdown blktrace in disk_release(), this is safe

because blk_trace_remove() is reentrant.