katello-installer fails to start foreman-tasks on Red Hat Satellite 6

Issue

• katello-installer fails to start foreman-tasks service on Red Hat Satellite 6.

  Could not start Service[foreman-tasks]: Execution of '/sbin/service foreman-tasks start' returned 10: 
  Starting foreman-tasks: Some processes of foreman-tasks is already running. Some not. 
  Please stop foreman-tasks first.[FAILED]
  /Stage[main]/Foreman::Plugin::Tasks/Service[foreman-tasks]/ensure: change from stopped to running 
  failed: Could not start Service[foreman-tasks]: Execution of '/sbin/service foreman-tasks start' returned 10: 
  Starting foreman-tasks: Some processes of foreman-tasks is already running. Some not. 
  Please stop foreman-tasks first.[FAILED]