sync: fix reporting of failed local checkouts

The refactor to multiprocessing broke status reporting slightly when
checking out projects.  Make sure we mark the step as failed if any
of the projects failed, not just when --fail-fast is set.

Change-Id: I0efb56ce83b068b2c334046df3fef23d797599c9
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/299882


Reviewed-by: Michael Mortensen <mmortensen@google.com>
Tested-by: Mike Frysinger <vapier@google.com>