Multiprocess RQ workers (using supervisor) (#4371)

* launch and monitor multiple workers using supervisor

* run supervisord in non-daemon mode

* redirect all output to stdout/stderr

* no need to log supervisord's output because it is redirected to stdout anyway

* updated and less brittle healthcheck

* add supervisor healthchecks

* remove redundant supervisor installation as it is installed by pip

* add a 5 minute check gate

bin/docker-entrypoint

@@ -25,7 +25,10 @@ dev_scheduler() {
 worker() {
   echo "Starting RQ worker..."
 
-  exec /app/manage.py rq worker $QUEUES
+  export WORKERS_COUNT=${WORKERS_COUNT:-2}
+  export QUEUES=${QUEUES:-}
+  
+  supervisord -c worker.conf
 }
 
 dev_worker() {