T/P Test Fixes, master branch (2020.12.11.)

Made sure that run_tpcnv_legacy_test(...) and run_tpcnv_test(...) would not interfere with each other. By choosing different (cache) variable names in them for looking up the script skeletons that they each need. And at the same time adding a bunch of quotes around file/directory names, to make the code more robust with directory names containing spaces.

This is to fix ATEAM-684. Which was revealed (but not caused) by !38853 (merged).

To be on the safe side, let's run a full-unit-tests suite. (That would've revealed the problem in !38853 (merged) as well...)