[WIP] Fixes #31644 - check ping 503 retry

[jjeffers]

This adds a simple check for 503 http responses and then retries for a given number of times before failing.

Tested this locally by modifying /etc/httpd/conf.d/05-foreman-ssl.conf:

 <Location "/pulp/api/v3">
    ...
    ProxyPass  http://localhost:8080/
    ProxyPassReverse http://localhost:8080/
   ...
  </Location>

At port 8080 a simple web application returns a 503.

In some situations a pulp3 migration will fail because the environment might include pulp3 services that have started but are not yet serving requests. This change provides a little insurance in that case.

[theforeman-bot]

Issues: #31644

[jjeffers]

[test katello]

[jturel]

I see this is triaged for 3.18.3 but hasn't moved in a while. Still relevant?

[jjeffers]

I see this is triaged for 3.18.3 but hasn't moved in a while. Still relevant?

@jlsherrill @ehelms was the fix for this merged elsewhere?

[jlsherrill]

it was an installer/puppet module change. I think we can close this now !