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>

tools/elastic/docker-compose.elastic-override.yml

@@ -1,3 +1,4 @@
+---
 # Structure for the Elastic Stack docker configuration came from docker-elk:
 # https://github.com/deviantony/docker-elk
 # docker-elk is under the MIT License,
@@ -15,8 +16,8 @@ services:
       - "9300:9300"
     environment:
       ES_JAVA_OPTS: "-Xms1g -Xmx1g"
-    # networks: # add back in when a connection to tower_tools is possible
-    #   - docker_elk
+      # networks: # add back in when a connection to tower_tools is possible
+      #   - docker_elk
 
   logstash:
     build: elastic/logstash/