Fix send futures in FakeChannelSink to unbreak a unit test that deadlocks after a previous change.

core/src/test/java/com/google/bitcoin/core/FakeChannelSink.java

@@ -48,6 +48,7 @@ public class FakeChannelSink extends AbstractChannelSink {
             FakeChannel channel = (FakeChannel) event.getChannel();
             boolean offered = channel.events.offer(event);
             assert offered;
+            event.getFuture().setSuccess();
         }
     }
 }