Implement retype in HP LeftHand driver

This adds the ability to modify the
type of an existing HP LeftHand volume to
another type supported on the same backend.

Main use case for this is changing provisioning,
(full vs. thin), adaptive optimization and data
protections settings for a volume on-demand.

Change-Id: I78e53431708bcb3151c5dc4016e65d1a655e03c6
Implements: blueprint retype-support-for-hplefthand-driver
Merge "Implement retype in HP LeftHand driver"