Add support for working with multiple glusterfs volumes

This patch adds support for working with multiple glusterfs volumes
for the GlusterFS native protocol driver. Since the semantics and
mapping for native driver is different compared to GlusterFS NFS
driver, this patch refactors the native driver as a standalone
driver and fixes some flows to fit the native driver with the
Manila share flows.

A more recent version of glusterfs having SSL support is needed.

Change-Id: I567c7602e97c9d55551baa29f121c05da2985007
Closes-Bug: #1368669
Merge "Add support for working with multiple glusterfs volumes"