copr: rebuild indexes only when whooshee version was changed

We don't have the command

     copr-frontend update_indexes_required

in production yet, but this shouldn't be a problem since it will
return RC 2 and when rebuild is required, the command returns RC 1,
so both of them are non-zero.

roles/copr/frontend-cloud/tasks/main.yml

@@ -122,9 +122,18 @@
   when: devel|bool
   copy: src=robots.txt dest=/var/www/html/
 
+
+- name: register whether indexes rebuild is required
+  command: copr-frontend update_indexes_required
+  become: yes
+  become_user: copr-fe
+  register: update_indexes_required_result
+  changed_when: False
+
 - name: rebuild indexes
   command: ./manage.py update_indexes
   become: yes
   become_user: copr-fe
   args:
     chdir: /usr/share/copr/coprs_frontend/
+  when: update_indexes_required_result.rc != 0