If we reset the model, we need to delete old components as well.

Task-number: QTIFW-313

Change-Id: I2a761cd68d868dd35d022956c0c6662fa07919a5
Reviewed-by: Christian Stenger <christian.stenger@digia.com>
Reviewed-by: Kai Koehne <kai.koehne@digia.com>
Reviewed-by: Niels Weber <niels.weber@digia.com>