Implement resize volume method

Trove use Cinder as volume backend default and Cinder requires that volume must
in "available" status if wish to resize. So we should stop db firstly, then
detach volume from instance and resize volume. Finally, restart db in ease.

If resize volume failed, the instance may stuck into "RESIZE" status. Because
we have no idea to rescue the volume which is in "error_extending" by Cinder.

implement bp implement-volume-extend

Change-Id: Iff3b302a705917e0e27cd70edf6e1be1639f62d5
Merge "Implement resize volume method"