ci: fix worker startup issue by adding missing env vars and cleanup unused vars

ci: fix worker startup issue by adding missing env vars and cleanup unused vars

Workers are currently refusing to work:

  Unhandled Error
  Traceback (most recent call last):
    File "/opt/venv/lib/python3.11/site-packages/twisted/application/app.py", line 673, in run
      runApp(config)
    File "/opt/venv/lib/python3.11/site-packages/twisted/scripts/twistd.py", line 29, in runApp
      runner.run()
    File "/opt/venv/lib/python3.11/site-packages/twisted/application/app.py", line 370, in run
      self.application = self.createOrGetApplication()
    File "/opt/venv/lib/python3.11/site-packages/twisted/application/app.py", line 437, in createOrGetApplication
      application = getApplication(self.config, passphrase)
  --- <exception caught here> ---
    File "/opt/venv/lib/python3.11/site-packages/twisted/application/app.py", line 446, in getApplication
      application = service.loadApplication(filename, style, passphrase)
    File "/opt/venv/lib/python3.11/site-packages/twisted/application/service.py", line 404, in loadApplication
      application = sob.loadValueFromFile(filename, "application")
    File "/opt/venv/lib/python3.11/site-packages/twisted/persisted/sob.py", line 174, in loadValueFromFile
      codeObj = compile(data, filename, "exec")
  builtins.SyntaxError: keyword argument repeated: connection_string (buildbot.tac, line 49)

and we're not aware about it, so lets fix it by adding the same
environment variables we're actually using in production.

While at it, cleanup the unused container_verify_string variables.

Signed-off-by: Petr Štetiar <ynezz@true.cz>