Fix docker-publish-github to contain extraEnvironmentVars

Change-Id: Ib0a8b66ec5e6288e6051b75eaf23d240748a9443
diff --git a/jjb/docker-publish-github.yaml b/jjb/docker-publish-github.yaml
index 0551bac..c4fa695 100644
--- a/jjb/docker-publish-github.yaml
+++ b/jjb/docker-publish-github.yaml
@@ -67,7 +67,13 @@
           default: '{maintainers}'
           description: "The person that sould be notified if this job fails"
 
+      - string:
+          name: extraEnvironmentVars
+          default: '{extraEnvironmentVars}'
+          description: "Provide extra environment variables to the build"
+
     project-type: pipeline
     concurrent: true
+    extraEnvironmentVars: ""
 
     dsl: !include-raw-escape: pipeline/docker-publish.groovy