xfs/837: fix test to work with pre-metadir quota mount options

xfs/837: fix test to work with pre-metadir quota mount options

Prior to metadir, xfs users always had to supply quota mount options to
get quota functionality, even if the mount options match the ondisk
superblock's qflag state.  The kernel, in turn, required a writable
filesystem if any mount options were specified.  As a result, this test
fails on those old filesystems because the _scratch_mount fails.

Metadir filesystems reuse whatever's in qflags if no mount options are
supplied, so we don't need them in MOUNT_OPTS anymore.

Change the _scratch_mount to _try_scratch_mount and add configurable
golden output to handle this case.

Cc: fstests@vger.kernel.org # v2025.06.22
Fixes: e225772353e212 ("xfs: add mount test for read only rt devices")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Zorro Lang <zlang@kernel.org>