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.

We could create an issue for this (and the other comment in doNotification() function) or it is enough to have the "inline FIXME comment" in the source code file?