Server indexes should be negative for a broadcast operation
Server indexes should be negative for a broadcast operation

In order to address a server by server number we need to specify
a negative server index. If we specify a positive index then gocb
will interpret this as the replica server index for a particular
vbucket.

Change-Id: I956f2367935ccd2b9bbb3624677c8678d08d6f08
Reviewed-on: http://review.couchbase.org/63421
Reviewed-by: Brett Lawson <c8c4369773d7d7226e031f0c4af62e3f38a08510@gmail.com>
Tested-by: Michael Wiederhold <a17fed27eaa842282862ff7c1b9c8395a26ac320@couchbase.com>

brett19/gocb