Fix extra hover enter events being sent by QSGCanvas

Fix extra hover enter events being sent by QSGCanvas

This fixes two issues: when one item is entered it is getting the
enter event twice. When we are moving from two items that share the
same parent, the parent is getting enter event -- which shouldn't
happen.

Change-Id: If0fe6d64d1f7cfb8679ce11edda7c02dc3783f9a
Reviewed-on: http://codereview.qt.nokia.com/3860
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Alan Alpert <alan.alpert@nokia.com>