Small endpoint cleanup.

Motivation
----------
DISCONNECT was notified twice, which is not a problem because the state
code will not distribute it, but it does not belong in there.

Modifications
-------------
The duplicate call has been removed and minor javadocs have been added.

Change-Id: Ifc97cb92cfabf392a5a1ee7aeb6d516d95bdd4b8
Reviewed-on: http://review.couchbase.org/42705
Tested-by: Michael Nitschinger <michael.nitschinger@couchbase.com>
Reviewed-by: Simon Baslé <simon@couchbase.com>