phase1, phase2: don't mark the build failed if a non-critical step fails

phase1, phase2: don't mark the build failed if a non-critical step fails

Some steps are informative or optional (haltOnFailure=False), so it makes
no sense to mark the whole build as failed if such a step fails.

Depending on the case, we either mark the build as "warning"
(warnOnFailure=True) or as successful (warnOnFailure=False).

Signed-off-by: Baptiste Jonglez <git@bitsofnetworks.org>