Call onDrawn on main thread to delay the callback

It seems like calling the KeyguardService
onDrawn callback when turning on the screen
leads to a problem with unlocking the device
using adb command. Adding the delay back
to unblock the failing tests.

Bug: 262889647
Change-Id: Iefabd721ccea770a224bdb2e2ad2c4194eba5557
2 files changed