If we want to mark test tree items because of their file name
explicitly for removal we must not mark its children
recursively without looking at their content. (Grand-)Children
might have a different file and won't get updated ('unmarked')
when just parsing single files which in turn would lead to
sweeping them after parsing.

Task-number: QTCREATORBUG-18689
Change-Id: Ic28dda5652899308a71d2bd3c28a7fde89a08a0e
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>