Remove unused field (reported by clion)

Change-Id: I4c032ad49c6ea3cc7d1ac65fd72bc86ef3e6a40e
Reviewed-on: http://review.couchbase.org/41137
Reviewed-by: Dave Rigby <daver@couchbase.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>