CI: speed up and simplify build, remove unnecessary Python code, remove --eNB* parameter list
This cleans up the CI framework for running end-to-end tests, and
improves the integration with OAI code. Specifically
- cleanup build_oai and helpers to output all text, which is captured
better by the CI
- build some images in the Cluster-Build in parallel to increase speed
- remove all --eNB{,1,2}{IPAddress,UserName,Password} variables. Those
were indexed through "instance" and "server ID" and are replaced with
the actual node name. I consider further cleanup to introduce a
"global" XML file node name so we don't need this in each step and
instead define this once.
- individual cleanup