Allow users to perform conditional commands

[lstocchi]

Users should be allowed to execute a command after an event occurred in the cluster. Right now there is no way to achieve it with the extension. One has to create a script and execute it in the pipeline.
The idea is to have something like:

delaycondition: the event to wait before to run the command. It keep checking the condition and then run the command only when the condition is met.
timedout: the time to wait before to force the exit. if the condition is not met before this time the cmd will be skipped.