always spawn projector but only if it's present

Change-Id: I08bdc61bb55e1fde332bb93b59207090e3611d20
Reviewed-on: http://review.couchbase.org/43653
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>