Move taskbar clean up so that it only gets called when user swipes up to go home.

This fixes the bug where the flag gets set when user taps on nav handle, which
results in the taskbar animation playing.

Flag: N/A
Test: open app
      wait for taskbar to finish stashing*
      tap on nav handle
      nothing happens (desired affect)
      * I will address tapping on taskbar while its animating in a separate change
Bug: 292108880
Change-Id: I75870050225bdd951c69224d272d0bd5a3d6d4ea