add assertions for wait_for_state / wait_for_status methods

[snowch]

this is not valid:

hpecp epic_worker wait-for-state --state [ready] 

however, no errors are thrown even though --state (singular) is not a valid parameter.

We should allow the user to provide:

• --state onestate
• --states [onestate, anotherstate]

the user should provide either --state or --states. --states may be empty, i.e. []

similar for --status

This applies to all cli modules implementing wait_for_state / wait_for_status