Description of problem:
Monitor -> Tasks page giving ISE after I was clicking "Resume" like mad in Dynflow console


Version-Release number of selected component (if applicable):
satellite-6.2.8-4.0.el7sat.noarch


How reproducible:
1 of 1


Steps to Reproduce:
1. Register 33k systems
2. Schedule ReX on 22k of them and hard-restart satellite machine because
   it was stuck (more about this in different bug)
3. Now parent task (and individual sub-tasks as well) are paused, so go to
   parent task and click 'Resume'
   https://<sat>/foreman_tasks/tasks/4ce98731-9e2c-462a-b4d4-9bc580054274
4. This does not change anything, so go to dynflow console and click 'Skip'
   on '2: Actions::RemoteExecution::RunHostsJob'
   https://<sat>/foreman_tasks/dynflow/1ea90878-8541-4509-b543-17ddf6e3fc38
5. Then click 'Resume' and because no state change happens, click it again
   and again quickly


Actual results:
Notice you get info message like "Task have to be paused to be able to resume it".
Now go to Monitor -> Tasks and notice ISE there "Oops, we're sorry but something went wrong searching: execution_plan by: {:uuid=>"aa5d4798-29f9-4c09-9524-ad338dda5637"}"


Expected results:
There should be no ISE.