Fixed issue when looking for backported changes

We were loking only on gerrit, ignoring commits that bypassed the gerrit review
system, now we also check on the git logs if the change is not found on gerrit
itself.

Change-Id: Id017b1f4c0ce83336fab5081a4981b83c1669082
Signed-off-by: David Caro <dcaroest@redhat.com>