Adds status progression verification behaviors for volumes.

* Adds verify_volume_status_progression() to volumes behaviors.
  (Verifies that volume goes from creating to available state.)
* Adds verify_volume_status_progression_during_attachment() to volume
  attachments behaviors.
  (Verifues that volume goes through available->attaching->in-use)
* Supports skipping states that may be transient enough to be missed
  by api-polling.
* Adds get_volume_status() behavior. (Code refactored out of
  wait_for_volume_status() code).

Change-Id: I74176edd4a47243aed95e2f594c4df9ba8b2aaf6
Merge "Adds status progression verification behaviors for volumes."