Fix ansible<2.8.0 bug

groups.tester|first, when Ansible is < 2.8.0, is being evaluated
even if groups.undercloud is defined.

Change-Id: Ie66c0760b705a74311769b9da009e7344de68bdd

main.yml

@@ -2,9 +2,11 @@
 - name: Set tester node
   hosts: localhost
   tasks:
+    # TODO: change groups.tester to groups.tester|first when Ansible will be updated to at least 2.8.0 as there is a bug in ansible < 2.8.0
+    # where groups.tester|first causing 'name' value to evaluate groups.tester even if groups.undercloud is defined
     - name: Add chosen node to tester group
       add_host:
-          name: "{{ install.get('tester', {}).get('node', {})|default(groups.undercloud|first, true)|default(groups.tester|first) }}"
+          name: "{{ install.get('tester', {}).get('node')|default(groups.get('undercloud', {})|first, true)|default(groups.tester, true) }}"
           groups: "tester"
     - include_role:
           name: inventory-update