Also trigger beforefeaturemodified event in non-standalone mode

d2a32d5 accidently changed the number of assertions in the
test_selectFeature function, so the change in behavior that no
beforefeaturemodified event is called any more in non-standalone mode got
unnoticed: Before unhacking ModifyFeature, the SelectFeature control
called the beforeSelectFeature method directly. Now, without a built-in
SelectFeature control, we need to call it from the selectFeature method in
both standalone and non-standalone mode.