revert back to v2 api

Signed-off-by: Clement Verna <cverna@tutanota.com>

inventory/group_vars/osbs-masters-stg

@@ -108,7 +108,7 @@ _osbs_reactor_config_map:
     - v2
 
     registries:
-    - url: https://candidate-registry.stg.fedoraproject.org/
+    - url: https://candidate-registry.stg.fedoraproject.org/v2
       insecure: False
       auth:
         cfg_path: /var/run/secrets/atomic-reactor/v2-registry-dockercfg