Before this commit the concurrent session wrapper mainly protected the
sending of messages. The close itself however may also cause a message
to be sent as is the case of the SockJS protocol.
This change protects the close and checks if the session has exceeded
send time or buffer limits in which case the close status is changed
to SESSION_NOT_RELIABLE (introduced in commit cbd5af3a) which in turn
signals that extra care should be exercised when closing the session.
Issue: SPR-13904
Rossen Stoyanchev
09a40b8a08