[CORD-2874]
Fix deprecation warnings raised by Ansible 2.5

Change-Id: Icb607d267af2771b046b46399ce5f0d182f629ab
diff --git a/roles/head-prep/tasks/main.yml b/roles/head-prep/tasks/main.yml
index 3fcb40a..4bb2bca 100644
--- a/roles/head-prep/tasks/main.yml
+++ b/roles/head-prep/tasks/main.yml
@@ -30,7 +30,7 @@
   with_items:
     - "{{ ansible_apt_repo | default('ppa:ansible/ansible') }}"
   register: result
-  until: result | success
+  until: result is success
   retries: 3
   delay: 10