8906 uts: illumos rootfs should support salted cksum

illumos/illumos-gate@0dd498c0020c4a0dd34d350b07f97399a475d102

Reviewed by: C Fraire <cfraire@me.com>
Reviewed by: Robert Mustacchi <rm@joyent.com>
Reviewed by: Yuri Pankov <yuripv@yuripv.net>
Approved by: Dan McDonald <danmcd@joyent.com>
Author: Toomas Soome <tsoome@me.com>