MFV r297505:
6739 userland version of cv_timedwait_hires() always assumes absolute time

Reviewed by: Paul Dagnelie <pcd@delphix.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Dan McDonald <danmcd@omniti.com>
Reviewed by: Robert Mustacchi <rm@joyent.com>
Approved by: Robert Mustacchi <rm@joyent.com>
Author: George Wilson <george.wilson@delphix.com>

illumos/illumos-gate@41c6413cb54bf338d7a59ed789ec2e0e44c35e6f