Fix disconnect logic for upr connections

When an upr connection is disconnected we should immediately
remove that connection from the upr connection map.

Change-Id: Ic4c7615adadb30952d261b6e6dd56576c7306cff
Reviewed-on: http://review.couchbase.org/30025
Reviewed-by: Chiyoung Seo <chiyoung@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>
Add stream end implementation for upr producer

For now if we have a stream just send a stream end message and
close that stream.

Change-Id: I301f08b408b8ecd66fd160785543811a3022a10c