Merge pull request #2175 from edx/feanil/when_to_tag

Change when we tag instances.

playbooks/roles/edx_service/tasks/main.yml

@@ -161,7 +161,7 @@
     tags:
       - Name: version:{{edx_service_name}}
         Value: "{{ item.0.DOMAIN }}/{{ item.0.PATH }}/{{ item.0.REPO }} {{ item.1.after |truncate(7,True,'') }}"
-  when: item.1.after is defined and ansible_ec2_instance_id is defined and edx_service_repos is defined
+  when: item.1.after is defined and COMMON_TAG_EC2_INSTANCE and edx_service_repos is defined
   with_together: 
     - edx_service_repos
     - code_checkout.results