For a deployment behind a firewall/proxy server some additional
environment settings should be passed along, for containers
such as magnum

This commit adds three new properties;
 container_http_proxy
 container_https_proxy
 container_no_proxy

In particular, the user will want to set container_http_proxy
and container_https_proxy properties with the proxy server
details.

Closes-Bug: #1628335
Change-Id: I0950a0467b4b68c38b13875eaf9cd433e64363cf