test_queue: Ensure the test_suite queue exists in setUp.
test_queue: Ensure the test_suite queue exists in setUp.

queue_client.queues does not list all the queues that exist on the
server (you can’t do that over AMQP); the condition "test_suite" in
queue_client.queues was always false.  So the test_suite queue could
accumulate extra messages that broke test_queue_error_json.

Signed-off-by: Anders Kaseorg <dfdb7392591db597bc41cf266a9c3bc12a2706e5@zulip.com>

zulip/zulip,kou/zulip,andersk/zulip,zulip/zulip,kou/zulip,andersk/zulip,rht/zulip,kou/zulip,kou/zulip,andersk/zulip,kou/zulip,andersk/zulip,zulip/zulip,kou/zulip,zulip/zulip,zulip/zulip,kou/zulip,andersk/zulip,zulip/zulip,rht/zulip,rht/zulip,rht/zulip,rht/zulip,andersk/zulip,andersk/zulip,rht/zulip,zulip/zulip,rht/zulip