[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