fix tracking of removed artifacts
fix tracking of removed artifacts

When going up the chains of parents we have to check the inputs of the
transformers and not only the parent's children.
The parent's children also contain dependencies, that have been
generated by the dependency scanners.

Task-number: QBS-100

Change-Id: I81aeb00a573bc390a78f5be697470ef9babc6cb3
Reviewed-by: Christian Kandeler <3aa99dcdd3f0cac61fb81c2a11771c0cc2497607@nokia.com>
Reviewed-by: Joerg Bornemann <47777b9406dbddd02a3fdca8341789a013805a11@nokia.com>

gatzka/qt-labs-qbs,gatzka/qt-labs-qbs,qtproject/qt-labs-qbs,qt-labs/qbs,villytiger/qbs,gatzka/qt-labs-qbs,gatzka/qt-labs-qbs,Distrotech/qbs,Distrotech/qbs,Distrotech/qbs,villytiger/qbs,villytiger/qbs,qtproject/qt-labs-qbs,qtproject/qt-labs-qbs,Distrotech/qbs,Distrotech/qbs,qtproject/qt-labs-qbs,Distrotech/qbs,villytiger/qbs,gatzka/qt-labs-qbs,qt-labs/qbs,qt-labs/qbs,qt-labs/qbs,villytiger/qbs,gatzka/qt-labs-qbs,qt-labs/qbs,qtproject/qt-labs-qbs,qtproject/qt-labs-qbs,gatzka/qt-labs-qbs,qt-labs/qbs,qtproject/qt-labs-qbs,villytiger/qbs,Distrotech/qbs,qt-labs/qbs