Candlepin service fails after upgrading from Red Hat Satellite 6.9 to 6.10

Issue

• After upgrading from 6.9 to 6.10, hammer ping shows candlepin and candlepin_auth / candlepin_events services as not running.

  candlepin:        
  Status:          FAIL
  Server Response: Message: 404 Not Found
  candlepin_auth:   
  Status:          FAIL
  Server Response: Message: Katello::Errors::CandlepinNotRunning
  candlepin_events: 
  Status:          FAIL
  message:         Not running
  Server Response: Duration: 2ms
  
  

• After upgrading to the 6.10 Red Hat Satellite dashboard page shows the following error:

  Oops, we're sorry but something went wrong Katello::Errors::CandlepinNotRunning
  

• satellite-maintain health check failing on server-ping after upgrading it to Red Hat Satellite 6.10.

  # satellite-maintain health check
  Running ForemanMaintain::Scenario::FilteredScenario
  --------------------------------------------------------------------------------
  Check whether all services are running using the ping call:           [FAIL]
  Couldn't connect to the server: undefined method `to_sym' for nil:NilClass
  --------------------------------------------------------------------------------