xfs: fix tests that try to access the realtime rmap inode

xfs: fix tests that try to access the realtime rmap inode

The realtime rmap tests were added to fstests a long time ago.  Since
they were added, we decided to create a metadata file directory
structure instead of adding more fields to the superblock.  Therefore,
fix all the tests that try to access these paths.

While we're at it, fix xfs/409 to run the *online* scrub program like
it's supposed to.  xfs/408 is the fuzzer for xfs_repair testing.

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