Changing the splitting for EventBased workflows

[paorozo]

We need to disable the option to change the splitting for tasks having the EventBased splitting algorithm.
@dabercro @areinsvo, maybe this check would be easier at the recovery tool's side, I am not sure how can the actor communicate there was a mistake with the parameter the operator sent.

[areinsvo]

Hmm. In theory this check was already implemented. It should simply fail to execute the action and throw up a Unified critical message, which I would then report to you. Here is where the check is applied. I'll have to figure out why it didn't work, unless maybe @prozober or @vlimant see the problem?
https://github.com/CMSCompOps/WmAgentScripts/blob/5c0c238562af864091e5a664a4d9d0591e111158/Unified/actor.py#L77