Add API support for rebuilding BFV instances

This adds a microversion and API support for triggering a rebuild
of volume-backed instances by leveraging cinder functionality to
do so.

Implements: blueprint volume-backed-server-rebuild
Closes-Bug: #1482040

Co-Authored-By: Rajat Dhasmana <rajatdhasmana@gmail.com>

Change-Id: I211ad6b8aa7856eb94bfd40e4fdb7376a7f5c358

doc/api_samples/versions/versions-get-resp.json

@@ -22,7 +22,7 @@
                 }
             ],
             "status": "CURRENT",
-            "version": "2.92",
+            "version": "2.93",
             "min_version": "2.1",
             "updated": "2013-07-23T11:33:21Z"
         }