xfs/509: adjust inumbers accounting for metadata directories

xfs/509: adjust inumbers accounting for metadata directories

The INUMBERS ioctl exports data from the inode btree directly -- the
number of inodes it reports is taken from ir_freemask and includes all
the files in the metadata directory tree.  BULKSTAT, on the other hand,
only reports non-metadata files.  When metadir is enabled, this will
(eventually) cause a discrepancy in the inode counts that is large
enough to exceed the tolerances, thereby causing a test failure.

Correct this by counting the files in the metadata directory and
subtracting that from the INUMBERS totals.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>