modify kv_sender as per latest projector

- kv_sender modified to reflect changes required by
  projector (same as tools/datapath.go)
- modify constants to more appropriate values

Change-Id: Iba7f24dd83c5c937770345d0671156d40c868acf
Reviewed-on: http://review.couchbase.org/39080
Reviewed-by: Sriram Melkote <siri@couchbase.com>
Reviewed-by: Deepkaran Salooja <deepkaran.couchbase@gmail.com>
Tested-by: Deepkaran Salooja <deepkaran.couchbase@gmail.com>