common/fuzzy: fix some problems with the online repair strategy

common/fuzzy: fix some problems with the online repair strategy

While auditing the fuzz tester code, I noticed there were numerous
problems with the online repair strategy -- the stages of the strategy
are not consistently logged to the kernel log, some of the error
messages don't identify /which/ scrubber we're calling, and we don't
actually re-run online scrub after a repair to make sure that it's
verification is ok.  Disable xfs_repair prefetch to reduce the chances
of an OOM kill, and abort the fuzz test if we can't mount.  We also
reorganize the error messages to make reading the golden output easier.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Zorro Lang <zlang@redhat.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>