Adds scenario tests for volume encryption

Two scenario tests and the supporting methods in the test manager
are added. For each encryption type, the test creates an image, boots an
instance of the image, creates an encryption type, creates a volume of that
type, attaches the volume to the instance, detaches it, and deletes
the encrypted volume and volume type.

Change-Id: Ib2c3f9b04d35a65ce2f0e45e63e940ecd92991d0
Implements: blueprint cinder-volume-encryption-tempest-tests
2 files changed