midonet: Provide has_neutron_plugin_security_group

Change-Id: I6ac12022bb8998fbec17cfa503db9277aa2eb8b7
Partial-Bug: #1458871

lib/neutron_plugins/midonet

@@ -1,4 +1,10 @@
 #!/bin/bash
 
-# REVISIT(devvesa): This file is intentionally left empty
-# in order to keep Q_PLUGIN=midonet work.
+# REVISIT(devvesa): This file is needed so Q_PLUGIN=midonet will work.
+
+# FIXME(yamamoto): This function should not be here, but unfortunately
+# devstack calls it before the external plugins are fetched
+function has_neutron_plugin_security_group {
+    # 0 means True here
+    return 0
+}