xfs_scrub: don't call phase_end if phase_rusage was not initialized

xfs_scrub: don't call phase_end if phase_rusage was not initialized

If unicrash_load() fails, all_pi can be used uninitialized in
phase_end(). Fix it by going to the unload: section if unicrash_load
fails and just go with unicrash_unload() (the is_service won't be
initialized here).

Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Bill O'Donnell <bodonnel@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrey Albershteyn <aalbersh@redhat.com>