[buildbot] Disallow non ABC members from summoning builds with a docker configuration

Summary:
This restricts the access to website previews to ABC members only. This policy might be relaxed in the future.

Depends on D13661.

Test Plan:

./contrib/teamcity/build-configurations.py check-buildbot

Reviewers: #bitcoin_abc, sdulfari

Reviewed By: #bitcoin_abc, sdulfari

Differential Revision: https://reviews.bitcoinabc.org/D13663