MB-8903: Start UPR in group and not the updater

Starting the upr conection in the group makes more sense
as it is one connection per group anyway.

Change-Id: I1e6bd1ba489aeda9d72af1adbf1b47fec0befad4
Reviewed-on: http://review.couchbase.org/30545
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Filipe David Borba Manana <fdmanana@gmail.com>