Start closing the device immediately in unfold transition test

Test testFoldImmediatelyAfterUnfold_runsFoldAnimation
should check that we continue animating the transition
even if we started folding the device immediately
after unfolding a foldable device.

There was a race condition between finishing the animation
and sending 'start closing' update, the test was failing
when 'start closing' update arrived after finishing
the transition because this will result into
running a separate 'fold' transition and the test
expects to have only one transition.

Fixed by sending the closing event immediately, in the same
stack frame, without extra delay.

Fixes: 259839615
Test: atest SystemUITests:com.android.systemui.unfold.progress.PhysicsBasedUnfoldTransitionProgressProviderTest#testFoldImmediatelyAfterUnfold_runsFoldAnimation
Change-Id: Id8ad81d6dfcef0802c4e0f8a66e5724cfc98de34