[#2586] Use correct EventExecutor to notify for bind failures on late registration

Motivation:

We used the wrong EventExecutor to notify for bind failures if a late registration was done.

Modifications:

Use the correct EventExecutor to notify and only use the GlobelEventExecutor if the registration fails itself.

Result:

The correct Thread will do the notification.
Code-inspection fixes

Motivation:

Saw some code-inspection warnings

Modifications:

Fix warnings

Result:

Less code-inspection warnings
Avoid redundant reads of head in peakNode

Motivation:

There is not need todo redunant reads of head in peakNode as we can just spin on next() until it becomes visible.

Modifications:

Remove redundant reads of head in peakNode. This is based on @nitsanw's patch for akka.
See https://github.com/akka/akka/pull/15596

Result:

Less volatile access.
Allow efficient writing of CompositeByteBuf when using native epoll transport.

Motivation:

There were no way to efficient write a CompositeByteBuf as we always did a memory copy to a direct buffer in this case. This is not needed as we can just write a CompositeByteBuf as long as all the components are buffers with a memory address.

Modifications:

- Write CompositeByteBuf which contains only direct buffers without memory copy
- Also handle CompositeByteBuf that have more components then 1024.

Result:

More efficient writing of CompositeByteBuf.