Pages: enable proper readiness probe
What does this MR do?
Enable a proper readiness probe for the GitLab Pages chart.
To do this, we've configured things such that statusUri defaults to
/-/readiness, and expose listen-http on 9090 when not otherwise
configured. We direct the readiness probe to the combination of these
to, such that it can be seen as one of:
- 
0.0.0.0:8090ifexternalHttpis present
- 
0.0.0.0:9090if any other configuration (static default)
Related issues
Relates to #2447 (closed)
Checklist
See Definition of done.
For anything in this list which will not be completed, please provide a reason in the MR discussion.
Required
- 
Merge Request Title and Description are up to date, accurate, and descriptive 
- 
MR targeting the appropriate branch 
- 
MR has a green pipeline on GitLab.com 
Expected (please provide an explanation if not completing)
- 
Test plan indicating conditions for success has been posted and passes 
- 
Documentation created/updated 
- 
Tests added 
- 
Integration tests added to GitLab QA 
- 
Equivalent MR/issue for omnibus-gitlab opened 
Edited  by Mitchell Nielsen