=act #3389 Improve SSL closing sequence

* Port of this fix in Spray by @jrudolph from this pull request https://github.com/spray/spray/pull/400
Merge pull request #1679 from akka/wip-3389-fix-ssl-engine-shutdown-ban

=act #3389 Improve SSL closing sequence
=act fix reference.conf comment for event-handler-startup-timeout
Merge remote-tracking branch: upstream/master