Handle branches or refs in job specification.

Change-Id: If46832e6c1d5538fad88c9503c248372cb5b9416
Reviewed-on: https://review.openstack.org/14096
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Approved: James E. Blair <corvus@inaugust.com>
Tested-by: Jenkins

zuul/model.py

@@ -339,7 +339,9 @@ class Job(object):
         if not self.branches:
             return True
         for branch in self.branches:
-            if branch.match(change.branch):
+            if hasattr(change, 'branch') and branch.match(change.branch):
+                return True
+            if hasattr(change, 'ref') and branch.match(change.ref):
                 return True
         return False