Revert "CTest: fix pre and post test commands with spaces" (#13887)

This reverts commit 6187876dea89618044e200808bcae75a18bd4043.

It was actually possible before to have paths with spaces in them, the spaces
just need to be quoted. This way spaces will work as argument separators.
Merge topic 'memcheck_pre_post_args' into next

c0756b6 Revert "CTest: fix pre and post test commands with spaces" (#13887)