http2: settle pending write callbacks on stream destroy

lib/internal/http2/core.js

@@ -2721,6 +2721,15 @@ class Http2Stream extends Duplex {
         });
       }
     }
+
+    // A write in flight may never get its native completion callback once the
+    // stream tears down; settle it so the Writable can clean up.
+    if (state.writeCb !== null) {
+      const writeCb = state.writeCb;
+      state.writeCb = null;
+      state.writePending = 0;
+      writeCb(err);
+    }
     callback(err);
   }
   // The Http2Stream can be destroyed if it has closed and if the readable

test/parallel/test-http2-close-while-writing.js

@@ -29,11 +29,21 @@ server.on('session', common.mustCall(function(session) {
     stream.on('error', common.mustCall((err) => {
       assert.strictEqual(err.code, 'ERR_HTTP2_STREAM_ABORTED');
     }));
-    stream.resume();
+
+    // Every write dispatched before close must have its callback invoked.
+    let writes = 0;
+    let writeCallbacks = 0;
     stream.on('data', function() {
-      this.write(Buffer.alloc(1));
+      writes++;
+      this.write(Buffer.alloc(1), () => {
+        writeCallbacks++;
+      });
       process.nextTick(() => client_stream.destroy());
     });
+    stream.on('close', common.mustCall(() => {
+      assert.strictEqual(writeCallbacks, writes);
+    }));
+    stream.resume();
   }));
 }));