Replace nova client with cinder client to use volume

Now cinder support a few new features like extend volume which used in Trove.
We can't use nova client to enjoy this new feature, so we should change to use
cinder client as volume management.

implement bp implement-volume-extend

Change-Id: I4f9139bacd7d8b4c2538bff6aa54416b27c9026e
Merge "Replace nova client with cinder client to use volume"