xfs_scrub: only retry non-permanent repair failures

xfs_scrub: only retry non-permanent repair failures

If a repair fails, we want to retry the repair if the error was a
transient one, such as ENOMEM.  For "permanent" ones (shutdown fs,
repair not supported by kernel, readonly fs) there's no point to
retrying them so just error out immediately.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>