xfs/449: update test to know about xfs_db -R

xfs/449: update test to know about xfs_db -R

The realtime groups feature added a -R flag to xfs_db so that users can
pass in the realtime device.  Since we've now modified the
_scratch_xfs_db to use this facility, we can update the test to do exact
comparisons of the xfs_db info command against the mkfs output.

Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Zorro Lang <zlang@kernel.org>