6536 zfs send: want a way to disable setting of DRR_FLAG_FREERECORDS

Reviewed by: Anil Vijarnia <avijarnia@racktopsystems.com>
Reviewed by: Kim Shrier <kshrier@racktopsystems.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Approved by: Dan McDonald <danmcd@omniti.com>
Author: Andrew Stormont <astormont@racktopsystems.com>

illumos/illumos-gate@880094b6062aebeec8eda6a8651757611c83b13e