Fix incorrect Http2UpgradeClientConnection write.

Motivation:

Http2UpgradeClientConnection#write has two issues

- the returned promise/future is not completed by the delegate write
- the event SEND_BUFFERED_MESSAGES_EVENT can end the http request before all chunks have been written

Changes:

- return the actual future of the delegate write operation
- delay SEND_BUFFERED_MESSAGES_EVENT when the last chunk has been written

Author: vietj

vertx-core/src/main/java/io/vertx/core/http/impl/Http2UpgradeClientConnection.java

@@ -696,18 +696,26 @@ public boolean writeQueueFull() {
 
     @Override
     public Future<Void> writeBuffer(ByteBuf buf, boolean end) {
-      Promise<Void> promise = upgradingStream.getContext().promise();
       EventExecutor exec = upgradingConnection.channelHandlerContext().executor();
       if (exec.inEventLoop()) {
-        upgradingStream.writeBuffer(buf, end);
+        Future<Void> future = upgradingStream.writeBuffer(buf, end);
         if (end) {
           ChannelPipeline pipeline = upgradingConnection.channelHandlerContext().pipeline();
-          pipeline.fireUserEventTriggered(SEND_BUFFERED_MESSAGES);
+          future = future.andThen(ar -> {
+            if (ar.succeeded()) {
+              pipeline.fireUserEventTriggered(SEND_BUFFERED_MESSAGES);
+            }
+          });
         }
+        return future;
       } else {
-        exec.execute(() -> writeBuffer(buf, end));
+        Promise<Void> promise = upgradingStream.getContext().promise();
+        exec.execute(() -> {
+          Future<Void> future = writeBuffer(buf, end);
+          future.onComplete(promise);
+        });
+        return promise.future();
       }
-      return promise.future();
     }
 
     @Override