Airship modify github url var

Allows to pass the whole repo url for verifications
and specify the credentials to use in Github.

Change-Id: I1eed3a63496bd712a749305709f712875e1a9f55
diff --git a/jjb/airship/job_openstack_image_building.yml b/jjb/airship/job_openstack_image_building.yml
index bc66f99..6261f51 100644
--- a/jjb/airship/job_openstack_image_building.yml
+++ b/jjb/airship/job_openstack_image_building.yml
@@ -46,7 +46,7 @@
     pipeline-scm:
       scm:
       - git:
-          url: https://github.com/{ci_github_repo}.git
+          url: "{ci_github_repo}"
           credentials-id: "{ci_github_jenkins_credentials_id}"
           branches:
             - 'master'