Set the service_type for the builder

If we don't do this we can't lookup the endpoint.

Change-Id: I7eae87afc9e4d9ef9dd4f5877b71a4ebe299df0a

solumclient/builder/v1/client.py

@@ -19,6 +19,8 @@ from solumclient.openstack.common.apiclient import client
 class Client(client.BaseClient):
     """Client for the Solum v1 API."""
 
+    service_type = "image_builder"
+
     def __init__(self, http_client, extensions=None):
         """Initialize a new client for the Builder v1 API."""
         super(Client, self).__init__(http_client, extensions)