quota: clean out speculative preallocations when checking quota usage

quota: clean out speculative preallocations when checking quota usage

On XFS, the only reliable way to clean out speculative post-eof
preallocations, delayed allocations, and speculative cow preallocations
is to cycle the filesystem mount.  Since we're comparing the post-test
quota counts against a freshly quotacheck to look for leaks, it's fine
to cycle the mount.  This eliminates sporadic quota count failures when
running xfstests with quotas enabled.

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>