Implement extend volume functionality in Rbd

This implements the extend volume functionality for Rbd driver.

Implements: blueprint extend-rbd-volume
Change-Id: I7ddbd0dda742627e959ac672b125555225238030
Clean up Huawei tmp files from tests.

Remove tmp files created by Huawei tests.

Change-Id: Id2eb4034b7be9d76843659647387344914ce236a
Fixes: bug 1200416
Merge "Clean up Huawei tmp files from tests."
Merge "Implement extend volume functionality in Rbd"