fix: CI workflow prereqs

66cc304 changes to the same CI workflow definition as Bunny uses, but
the `before_build.sh` script was not adapted for it.

Author: fretb

bin/ci/before_build.sh

@@ -3,6 +3,12 @@
 CTL=${RUBY_RABBITMQ_HTTP_API_CLIENT_RABBITMQCTL:-"sudo rabbitmqctl"}
 PLUGINS=${RUBY_RABBITMQ_HTTP_API_CLIENT_RABBITMQ_PLUGINS:-"sudo rabbitmq-plugins"}
 
+case $CTL in
+  DOCKER*)
+    PLUGINS="docker exec ${CTL##*:} rabbitmq-plugins"
+    CTL="docker exec ${CTL##*:} rabbitmqctl";;
+esac
+
 echo "Will use rabbitmqctl at ${CTL}"
 echo "Will use rabbitmq-plugins at ${PLUGINS}"