xfs_scrub: don't report media errors for space with unknowable owner

xfs_scrub: don't report media errors for space with unknowable owner

On filesystems that don't have the reverse mapping feature enabled, the
GETFSMAP call cannot tell us much about the owner of a space extent --
we're limited to static fs metadata, free space, or "unknown".  In this
case, nothing is corrupt, so str_corrupt is not an appropriate logging
function.  Relax this to str_info so that the user sees a notice that
media errors have been found so that the user knows something bad
happened even if the directory tree walker cannot find the file owning
the space where the media error was found.

Filesystems with rmap enabled are never supposed to return OWN_UNKNOWN
from a GETFSMAP report, so continue to report that as a corruption.
This fixes a regression in xfs/556.

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