Bug/harness tests failing under valgrind

### Description
Better valgrind suite script (a few errors fixed).
Two functional tests that failed under valgrind only are now fixed (with a sleep - but only when running under valgrind).
An 'important' FIXME added, describing how to avoid 'false leak warnings' by valgrind.

Yes, you are right.
An issue would be good.
One more techdebt ... It keeps growing