Be more proactive about cleaning up exchanges declared here

Author: michaelklishin

test/src/com/rabbitmq/client/test/functional/AlternateExchange.java

@@ -98,6 +98,7 @@ public void handleReturn(int replyCode,
  protected void setupRouting(String name, String ae) throws IOException {
  Map<String, Object> args = new HashMap<String, Object>();
  if (ae != null) args.put("alternate-exchange", ae);
+ channel.exchangeDelete(name);
  channel.exchangeDeclare(name, "direct", false, false, args);
  channel.queueBind(name, name, name);
  }