generic/338: don't check fs after crashing it

generic/338: don't check fs after crashing it

This test tries to make the filesystem go down by setting up
dm-error and committing metadata updates.  Since the test doesn't
remount the fs after it goes down to recover the log, this can
result in a dirty log being presented to the post-test filesystem
check if the filesystem is xfs and quotas are enabled.

Since this is a regression test for a NULL pointer dereference in
the kernel after the fs goes down, simply skip the post-test fsck.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>