yamllint: Make all files in awx pass yamllint

This commit updates all files that weren't passing yamllint for them to
pass.

A new yamllint target has been added. One can run `tox -e yamllint` or
`yamllint -s .` locally to ensure yaml files are still passing.

This check will be enabled in the CI so it can get on every new
contributions, and prevent merging non-compliant code.

Signed-off-by: Yanis Guenane <yguenane@redhat.com>

installer/roles/kubernetes/tasks/backup.yml

@@ -55,7 +55,7 @@
           --port={{ pg_port | default('5432') }} \
           --username='{{ pg_username }}' \
           --dbname='{{ pg_database }}'" > {{ playbook_dir }}/tower-openshift-backup-{{ now }}/tower.db
-  no_log: yes
+  no_log: true
 
 - name: Copy inventory into backup directory
   copy: