Increased TTL interval.

On my machine 1 sec interval is fine, but it start failing around half a
second. Hopefully this will be enough for the CI server.

Author: Francesco Mazzoli

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

@@ -310,7 +310,7 @@ private void ttlTest(final long ttl) throws Exception {
         Map<String, Object> args = new HashMap<String, Object>();
         args.put("x-message-ttl", ttl);
         deadLetterTest(new Runnable() {
-                public void run() { sleep(ttl + 1000); }
+                public void run() { sleep(ttl + 1500); }
             }, args, "expired");
     }