Fixes #27229 - add message attribute to ping api

[amirfefer]

Related to #8039

ping API call doesn't return messages, so

Katello::Ping.ping[:services]

returns:

{:pulp=>{:status=>"FAIL", :message=>"Not all necessary pulp workers running at https://centos7-devel.tlv-fedora25.example.com/pulp/api/v2/."},
 :pulp_auth=>{:status=>"FAIL", :message=>"Skipped pulp_auth check after failed pulp check"}, 
:candlepin=>{:status=>"ok", :duration_ms=>"56"},
 :candlepin_auth=>{:status=>"ok", :duration_ms=>"26"}, 
:foreman_tasks=>{:status=>"ok", :duration_ms=>"18373"}}

while the api (/api/ping) returns:

  {"status":"FAIL","services":{"pulp":{"status":"FAIL"},"pulp_auth":{"status":"FAIL"},
"candlepin":{"status":"ok","duration_ms":"19"},
"candlepin_auth":{"status":"ok","duration_ms":"14"},
"foreman_tasks":{"status":"FAIL"}}}

[theforeman-bot]

Issues: #27229

[waldenraines]

@jlsherrill any reason we shouldn't do this?

[jlsherrill]

nope, thanks @amirfefer !