do not return url in the "from" field of view_merger error record

because it can contain user:pasword@ and overall contains too much
internal info for user to know

return host:port instead so the user knows which node had a problem

Change-Id: Ia7d401ba70161cf79afabe899b0e24e6331c30a2
Reviewed-on: http://review.couchbase.org/43382
Tested-by: Artem Stemkovski <artem@couchbase.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Sarath Lakshman <sarath@couchbase.com>
Reviewed-by: Volker Mische <volker.mische@gmail.com>