xfs_repair: improve error reporting when checking rmap and refcount btrees

xfs_repair: improve error reporting when checking rmap and refcount btrees

When we're checking the rmap and refcount btrees, push error reporting
down to the exact locations of failures so that the user sees both a
message specific to the failure that occurred and what repair was doing
at the time.  This also removes quite a bit of return code handling,
since all the errors were fatal anyway.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
[sandeen: update subject and change to djwong's updated commit log]
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>