PhoneWindowManager: Fix a couple of issues and cleanup recent PIE rewamp

SystemGestures is unregistered due to default new EdgeGestureService,
still for safety keep a boolean check on requestTransientBars().
Refresh height live.

Change-Id: Iae9c6079c21e65d01eea330fa17f3861a4c2e100
Signed-off-by: Carlo Savignano <stevewatersy@gmail.com>