Make deploy-ci-overcloud script configurable

Pulls almost all values in from the json env files. Left alone a few
exceptions that I don't see us actually needing to configure at this
point.

Aside from setting the region name to hp1, this script contains no
hardcoded defaults - it assumes that the hp1 config files will be around
to provide the values for that region.

Change-Id: Ie5876222dbd01e18a7e81aa1c3cb92407b9206ed
Merge "Make deploy-ci-overcloud script configurable"