Integrate pjdfstest test suite execution into kyua

pjdfstest execution is opt-in and must be done as root due to some of the
assumptions made by the test suite and lack of error checking in the non-root
case

A description of how to execute pjdfstest with kyua is provided in
share/pjdfstest/README

Phabric: D824 (an earlier prototype patch)
MFC after: 1 month
Relnotes: yes
Sponsored by: EMC / Isilon Storage Division