Add integration tests for Locate using new attributes

This change adds integration tests that verify that objects can
be found by Locate when filtering off of the new ObjectGroup and
ApplicationSpecificInformation attributes. Some minor tweaks to
the database attribute models are included to simplify usage.

kmip/services/server/engine.py

@@ -799,6 +799,8 @@ class KmipEngine(object):
                     )
             elif attribute_name == "Object Group":
                 for value in attribute_value:
+                    # TODO (peterhamilton) Enforce uniqueness of object groups
+                    # to avoid wasted space.
                     managed_object.object_groups.append(
                         objects.ObjectGroup(object_group=value.value)
                     )