freshmaker: whitelist testmodule on stage

inventory/group_vars/freshmaker-stg

@@ -2,7 +2,6 @@
 # For app config
 freshmaker_messaging_topic_prefix:
 - org.fedoraproject.stg
-- org.fedoraproject.prod
 
 freshmaker_parsers:
 - freshmaker.parsers.git:GitReceiveParser
@@ -21,3 +20,9 @@ freshmaker_admins:
 
 freshmaker_dry_run: True
 freshmaker_log_level: debug
+
+freshmaker_handler_build_whitelist:
+  global:
+    module:
+    - name:
+      - testmodule