REACH-40 Profile UI speed in Dynamo/Flood

While profiling Flood UI speed we found out that in some cases we got more responses from server than we asked for. This was happening because some times event was not unbound correctly. So in this PR I remove event binding each time RunCancelComand received and now we bind event only once on webserver start.
I guess you can further optimize this to:

```cs
var nodes = GetExecutedNodes();
if ((nodes == null) || !nodes.Any())
    return;
```

Does that make sense? Or does the client expects a return always, even with empty list?