Make resource check messages more consistent

This adds a method to be used in handle_check calls to make error
messages more consistent, as well as making sure that all unexpected
messages get displayed in the status_reason field, as opposed to
stopping on the first error.

Change-Id: Id855886ae42eabd78dafc6514eca9eebf905f291
Implements: blueprint stack-check
Merge "Make resource check messages more consistent"