Duplicate script execution from UI

[MJJoyce]

Ran into an issue with the monitoring UI where two instances of the same script executed when clicking the run button from the script control widget. The only way I could duplicate this was by double clicking the run button quickly before events propagated from the backend to the frontend and disabled the button functionality.

We should update 2 things on this. First, the backend should prevent attempts at running a script when another script is executing. This is arguably more useful to avoid two people from trying to run scripts and overlapping, but it also solves the encountered problem. Second, the execution control should be more intelligent about state tracking and preventing duplicate reactions. At the minimum, this should be on the script execute button.