Acknowledge Nova VERIFY_RESIZE as RESIZE state

After a resize, Nova changes instances to the VERIFY_RESIZE state,
which must be confirmed before they return to ACTIVE. However, as
far as Trove is concerned instances in VERIFY_RESIZE should still
report RESIZE until they're actually done. Additionally, instance
status unit tests are added to verify that the correct statuses
are reported.

Change-Id: I9c1824f8fe420025f329209c41c7aac1d8d7921c
Closes-Bug: #1217985
Merge "Acknowledge Nova VERIFY_RESIZE as RESIZE state"