Allow flags on stream request packets

Change-Id: Ic5c015d335790955ad40b8e74620a502d3d7f91c
Reviewed-on: http://review.couchbase.org/33310
Reviewed-by: Artem Stemkovski <artem@couchbase.com>
Tested-by: Artem Stemkovski <artem@couchbase.com>