Build container images in parallel

[dirgim]

This change introduces parallel builds in the playbooks/roles/os_temps/setup_containers.yml task in the following manner:

1. All the information needed to initiate a build (params, buildconfig and imagestream checks etc.) gets proccessed and stored in corresponding hashes (dictionaries) for every template before the parallel builds get initiated (setup_os_templates.yml)
2. The builds get started in (relatively) rapid succesion, only waiting to check if the build is started - this helps to stagger the builds if the number of concurrent builds gets too large to be run at the same time (handle_os_templates.yml which calls build_new_app.yml)
3. While the builds are running in parallel, the next step waits for the first build to be finished, and then for the second one and so on - the result of every build is stored in a separate hash (check_new_app.yml)
4. After all the builds are finished, the results of all the builds are checked and if any of them failed, all the failed build resources get cleaned up and the builds that failed get retried in another run which starts from the step 2. this gets repeated for a maximum of 4 times (handle_os_templates.yml)

In testing, building container images in parallel tended to be 40% faster on average than building them sequentially.

[psiroky]

LGTM - this is a great improvement! I can confirm the ~40% improvement when running CVP setups.

[arilivigni]

Does this also take care of cleanup issues?

[dirgim]

Only partially, I'm testing some additional cleanup fixes right now

[arilivigni]

Do you think we should wait and add it to this PR?

[dirgim]

I was thinking of making any major changes to cleanup a separate PR. This last commit is just a small fix.

[arilivigni]

LGTM