Add storage backends env files for containerized deployment

Add storage backends env files for containerized deployment

A storage backend has to be selected when deploying manila,
otherwise the manila-share service will fail to start. For this,
we have some environment files specifying the configuration for
different storage backends. We need a dockerized version
for this environment files.

In this patch set we add those environment files.

Change-Id: I9886016b02bec26699af1f8165d7b0702dfe8b9b
Partial-Bug: #1668922
(cherry picked from commit d7d54594410f60ea6ebf1301048d95f64c66f645)