Add debounce for hide animation of fixed rotation recents

If navigation bar is pressed, it may trigger recents animation with
fixed rotation, and if the touch is released immediately, the show/hide
animation will apply in a short time that looks blinking.

Bug: 160238664
Test: With 2 button navigation, launch a landscape activity and press
      home key. The status bar should fade out and fade in smoothly.

Change-Id: I2e92e614c95b30a1e5de53e28b4140a430015414