Apply cancellation policy to reserved nodes

Currently, in WFEngine.cancel_job() the cancellation policies (rerun or pause) are applied only to nodes in RUNNING state. It makes much sense to apply the policy also to node in RESERVED state.

policy	old state	new state
rerun	RUNNING	WAITING
rerun	RESERVED	WAITING
deactivate	RUNNING	DEFUSED
deactivate	RESERVED	PAUSED

We have to find out the benefits / drawbacks of DEFUSED vs. PAUSED and extend the test cases.