Clear existing streams from upr client if updater crash

If updater crash due to some reason, the next updater run
should not be affected. If updater crashes while reading from
a upr stream, the upr stream request will be active within the
upr client. We need to remove the active stream if updater exits
with an error.

Change-Id: I36ee7bf3ef7673cab2547762db7e3db5ae18c355
Reviewed-on: http://review.couchbase.org/38480
Reviewed-by: Volker Mische <volker.mische@gmail.com>
Tested-by: Sarath Lakshman <sarath@couchbase.com>