fix(controller): create directory only on create

If a modification is made to the app, then the underlying signal should
not tell etcd to re-create the directory or else etcd will complain that
you are trying to write to an already-existing directory.

Author: Matthew Fisher

controller/api/models.py

@@ -628,7 +628,8 @@ def _etcd_purge_user(**kwargs):
 
 def _etcd_create_app(**kwargs):
     appname = kwargs['instance']
-    _etcd_client.write('/deis/services/{}'.format(appname), None, dir=True)
+    if kwargs['created']:
+        _etcd_client.write('/deis/services/{}'.format(appname), None, dir=True)
 
 
 def _etcd_purge_app(**kwargs):