Fix config registration in cinder volume drivers.

Fix config registration in cinder volume drivers.

The config documentation relies on options being registered
on a modules import.  Our need to move the drivers to using
self.configuration for multi-backend support means that options
wouldn't be loaded until object initialization which breaks
documentation.

This patch puts a dummy CONF init/load back in the drivers. While putting
this change together I came across a number of drivers still using FLAGS,
and even worse a number of drivers using a mixture of FLAGS and CONF and
self.configuraiton.  So most of those are cleaned up here as well.

Note there are two drivers that were not updated at all here:
  1. windows.py
  2. zadara.py

The zadara folks have indicated that they're in the process of updating and
releasing a new version of their driver so I left that as is.

The windows driver needs a bit of work to switch over.

Fixes bug: 1179159

Change-Id: I90165299bf080da17741d027e36e361540da0ff8