xfs/{030,033,178}: forcibly disable metadata directory trees

xfs/{030,033,178}: forcibly disable metadata directory trees

The golden output for thests tests encode the xfs_repair output when we
fuzz various parts of the filesystem.  With metadata directory trees
enabled, however, the golden output changes dramatically to reflect
reconstruction of the metadata directory tree.

To avoid regressions, add a helper to force metadata directories off via
MKFS_OPTIONS.

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