Test stability with minitest 5.11.3

[MSP-Greg]

Being a "always the most recent rev" type, I've been running testup-2 with minitest 5.11.3 & SU 2018.

There seems to be stability issues, where error results vary from run to run. I have seen this with other repos when minitest was updated.

Anyway, I think I've got them sorted out, but I'm wondering if anyone else has seen the same thing?

Notes: I'm omitting the TC_Geom_PolygonMesh class, as it it seems to stop the test run. One test's code line actually causes a 'Bug Splat'. More work on it later...

Current results are:

1706 runs, 3117 assertions, 12 failures, 1 errors, 38 skips

Thanks, Greg

Attached Failure/Error Summary Test Summary_2018-02-05.txt