JCBC-251: Allow replicas with index 0 to work.

This changeset makes sure that replicas on the first
node still get included in the observe broadcast. Before
this changeset, all replicas that live on the first node
will lead to a timeout because they never get included
and as a result can never report replicate success.

Change-Id: Ic5fc4602ed468bbbaaecc16932964782b6d1464f
Reviewed-on: http://review.couchbase.org/24817
Reviewed-by: Matt Ingenthron <matt@couchbase.com>
Tested-by: Michael Nitschinger <michael.nitschinger@couchbase.com>