http2: don't send trailers on a closed connection

There is a race condition between onStreamCloseResponse(), which
removes the wantTrailers listener, and Http2Stream.close(), which
will invalidate the connection. IE, sendTrailers can be called on
a closed connection which would crash with a:
Error [ERR_HTTP2_INVALID_STREAM]: The stream has been destroyed

PR-URL: #23146
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Trivikram Kamat <[email protected]>

Author: edevil

lib/internal/http2/core.js

@@ -330,7 +330,7 @@ function tryClose(fd) {
 function onStreamTrailers() {
   const stream = this[kOwner];
   stream[kState].trailersReady = true;
-  if (stream.destroyed)
+  if (stream.destroyed || stream.closed)
     return;
   if (!stream.emit('wantTrailers')) {
     // There are no listeners, send empty trailing HEADERS frame and close.