Remove need for CONF acces in brick iscsi

At some point we'd like brick to be a standalone lib,
and as such we don't want to have a requirement for
CONF files and having duplicate conf entries across
projects.

The better approach would be to let the projects decide
what they want to use, and how they want defaults to be set
and then pass those settings in via __init__ or when calling
the methods that need them.

Partial-Bug: #1230066

Change-Id: Ib108f1abb2948cb896bdad58070daa7a725a205d
Merge "Remove need for CONF acces in brick iscsi"