Fix regression in times for children of transformed layers.

The regression was introduced by dd4d3410a6c7a26878f7b204b6b5aa2872134bf0,
and shows up in the Sunrider tutorial battle, when the PACT ships
attack with missiles.

The problem was that we were adjusting the times improperly - using
AdjustTimes to make the adjustment. Instead, we want the MultiBox
containing the layer to make the adjustment (which it does when
layer_name is set). This is because the MultiBox handles start
and animation times that are not the time at which the layer
was shown.