proper ci options

Change-Id: I31615654c78f751117bf04875db8ccd72c86deab

gz3d/utils/Gruntfile.js

@@ -125,6 +125,12 @@ module.exports = function(grunt) {
         }
       }
     },
+
+    ci: {
+      options: {
+        gerritBranch: '<%= gerritBranch %>'
+      }
+    },
   });
 
   // Load grunt tasks automatically