fix issue with iteritems still used in one place

Cherry-picked from: d62eada1264f5f574394e3d6f1666a5f2d443f68

Change-Id: I1370af6bc375c4827ee79869fadc7a8a8744e9b7

adjutant/common/user_store.py

@@ -154,7 +154,7 @@ class IdentityManager(object):  # pragma: no cover
                     except AttributeError:
                         # Just means the assignment is a group.
                         pass
-            for user_id, user in users.iteritems():
+            for user in users.values():
                 user.roles = list(set(user.roles))
         except ks_exceptions.NotFound:
             return []