All API controllers inherit from wsgi.Controller

Most of the Cinder Public API Controllers inherit from wsgi.Controller,
but still some Cinder Public APIs controllers directly inherit from
object. So it's necessary to unify all the Cinder Public API Controllers
inherit from wsgi.Controller.
1. For code cleanup.
2. When we try to do body valid check in api's put/post method later, we
can use the helper function is_valid_body instead of using try...catch
block.

Change-Id: I88812224e0b182939cfccce63982cb8f95792891
Closes-Bug: #1257198
Merge "All API controllers inherit from wsgi.Controller"