Fix shade jumping back and forth when opening on shade/hub

The bouncer touch handler sets the legacy shade tracking state when a
touch session starts or stops. However, this happens on any touch while
the hub or dream are open, even if the touch handler does not capture
the gesture and start opening the bouncer.

When the state gets erroneously unset as the shade opening starts, the
shade code does not think the user is opening the shade and strange
things happen, causing the shade to jump back and forth between the
expected expansion and 100%.

Bug: 397578827
Fixed: 397578827
Test: atest BouncerSwipeTouchHandlerTest
      manually verified that opening shade looks smooth
Flag: NONE minor fix
Change-Id: I788f8f17826bafa7f353507dd6db3a1cdca9e9e9