OpenZFS 6580 - zfs-tests use undefined variable WRAPPER

OpenZFS 6580 - zfs-tests use undefined variable WRAPPER

Authored by: Yuri Pankov <yuri.pankov@gmail.com>
Reviewed by: John Kennedy <john.kennedy@delphix.com>
Approved by: Matthew Ahrens <mahrens@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Ported-by: George Melikov <mail@gmelikov.ru>
OpenZFS-issue: https://www.illumos.org/issues/6580
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/9498083
Closes #5789

Porting notes:
- deleted in ZoL: functional/utils_test/utils_test_007_pos.ksh