QmlDesigner: Disable componentComplete for primitive creation

Control are now in a qrc file and the component are registered as Qml
types. We are using the primitive creation path in this case so we have
to disable the componentComplete call.

Change-Id: I52936b92d936acbfc21ba800ffca9123fcece864
Reviewed-by: Thomas Hartmann <Thomas.Hartmann@digia.com>