Related: #3449
Motivation:
When a user shut down an EventExecutor/Loop prematurely, a Promise will
fail to execute its listeners. When it happens, DefaultPromise will log
a message at ERROR level, but there's no way to get notified about it
programmatically.
Modifications:
Do not catch and log the RejectedExecutionException unconditionally,
but only catch and log for non-late listener notifications, so that a
user gets notified on submission failure at least when the listener is
late.
Result:
Remedies #3449 to some extent, although we will need fundamental fix for
that, such as #3566
4fa5d2cf52