travis: Fix various bugs in new queue worker test.

* Now queue_workers.py sorts queue names and prints them on their own
  line.  Previously it's output was nondeterministic.
* Simplified grep strategy for removing the "test" worker.

scripts/lib/queue_workers.py

@@ -22,5 +22,5 @@
                         help="Specify which types of queues to list")
     args = parser.parse_args()
 
-    workers = get_active_worker_queues(args.queue_type)
-    print(" ".join(workers))
+    for worker in sorted(get_active_worker_queues(args.queue_type)):
+        print(worker)

tools/travis/production-helper

@@ -87,8 +87,9 @@ fi
 echo; echo "Now confirming all the RabbitMQ queue processors are correctly registered!"; echo
 # These hacky shell scripts just extract the sorted list of queue processors, running and expected
 supervisorctl status | cut -f1 -dR | cut -f2- -d: | grep events | cut -f1 -d" " | cut -f3- -d_ | cut -f1 -d- | sort -u > /tmp/running_queue_processors.txt
-for i in `/home/zulip/deployments/current/scripts/lib/queue_workers.py`; do echo $i | grep -v ^test$; done | sort > /tmp/expected_queue_processors.txt
-if diff /tmp/expected_queue_processors.txt /tmp/running_queue_processors.txt >/dev/null; then
+/home/zulip/deployments/current/scripts/lib/queue_workers.py | grep -v ^test$ > /tmp/expected_queue_processors.txt
+if ! diff /tmp/expected_queue_processors.txt /tmp/running_queue_processors.txt >/dev/null; then
+    set +x
     echo "FAILURE: Runnable queue processors declared in zerver/worker/queue_processors.py "
     echo "do not match those in puppet/manifests/zulip/base.pp"
     echo "See http://zulip.readthedocs.io/en/latest/queuing.html for details."