3991: Set workbench_address in docker config.
3991: Run passenger script using bundle exec.

Passenger was installed in a previous step, but that was done using
"bundle install", which installs into ./vendor/bundle instead of a
system-wide install dir. This way, we install the passenger version
listed in services/api/Gemfile.lock instead of installing some other
version (or failing completely).
3991: Handle "no workbench_address configured" more gracefully.

* Remove example config from default production section.
* Follow config rule: false = feature disabled, nil = sysadmin error.
* Respond 404 at root url if no workbench_address is configured.
* Never redirect to workbench if client requested JSON.
3991: Use db:structure:load and db:seed instead of db:setup: the database already exists here.
3991: Change docker default to "no root url redirect". Make "not found" message more friendly.
3991: Fix config checks in admin_notifier.
3991: Merge branch 'master' into 3991-docker-workbench-address
Merge branch '3991-docker-workbench-address' closes #3991