OpenZFS 6642 - testrunner output can be displayed in the wrong order

OpenZFS 6642 - testrunner output can be displayed in the wrong order

6643 zfstest should enforce the required privileges before running.
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Jonathan Mackenzie <jonathan.mackenzie@delphix.com>
Reviewed by: Yuri Pankov <yuri.pankov@nexenta.com>
Approved by: Robert Mustacchi <rm@joyent.com>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Reviewed by: John Kennedy <john.kennedy@delphix.com>
Ported-by: Brian Behlendorf <behlendorf1@llnl.gov
OpenZFS-issue: https://www.illumos.org/issues/6642
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/412db4e
Closes #5777

Porting notes:
- The 6643 changes were dropped a different version of this script
  is used to configure the environment under Linux.