Checking Red Hat Satellite 6 service status fails with error Unit name pulpcore-worker@.service is neither a valid invocation ID nor unit name is encountered

Issue

• Below error is encountered while checking the Red Hat Satellite 6 service status:

  Failed to get load state of pulpcore-worker@.service: Unit name pulpcore-worker@.service is neither a valid invocation ID nor unit name
  

• The same error is encountered while trying to upgrade the Satellite server

  Check whether all services are running:                               [FAIL]
  Following services are not running: pulpcore-worker@.service
  
  Continue with step [Restart applicable services]?, [y(yes), n(no)] y
  Restart applicable services:
  
  Stopping the following service(s):
  pulpcore-worker@.service
  \ stopping pulpcore-worker@.service
  Failed to stop pulpcore-worker@.service: Unit name pulpcore-worker@.service is missing the instance name.
  See system logs and 'systemctl status pulpcore-worker@.service' for details.
  Failed to get load state of pulpcore-worker@.service: Unit name pulpcore-worker@.service is neither a valid invocation ID nor unit name.
  \ All services stopped