Add a test case for LumiList just for one task, make it work

Fixes #5314 

You can now specify LumiList in a Task section and its set. Then the task iterator which sets it for every task in a WF is told to ignore it if it's already there. @amaltaro , please review.
No, this is the part of the code that propagates settings from the workload into each task in the workload. So if it was already set in that task, it skips setting it again. Take a look at the test case. I can revise the test case to have two tasks with different lists and a third list for the global list, but it should work just fine.

Tasks are created before the workload settings are propagated.