Fix metal3 container image job triggers

Change-Id: I5db7a87c24ef8147bd82440540b1cc528a98ee22
diff --git a/jjb/metal3/job_container_image_building.yaml b/jjb/metal3/job_container_image_building.yaml
index 96468fb..9ab8cfc 100644
--- a/jjb/metal3/job_container_image_building.yaml
+++ b/jjb/metal3/job_container_image_building.yaml
@@ -44,18 +44,8 @@
         num-to-keep: 300
         artifact-days-to-keep: -1
         artifact-num-to-keep: -1
-
-    scm:
-      - git:
-          url: "{repo}"
-          credentials-id: "{ci_github_jenkins_credentials_id}"
-          name: 'origin'
-          refspec: '+refs/heads/*:refs/remotes/origin/*'
-          wipe-workspace: True
-          honor-refspec: True
-          shallow-clone: False
-          included-regions:
-            - '${dockerfile_location}'
+    - github:
+        url: '{repo}'
 
     triggers:
       - github