Tweak to isOnLockscreen

With numerous notifs on the lockscreen and UDFPS set up,
tap a notification to show ALTERNATE_BOUNCER. During the
end of this transition, the bounds may flicker. This occurs
as there is a tiny gap between conditions in isOnLockscreen
flow. Use transitionValue() instead for all checks.

Fixes: 372210467
Test: atest SharedNotificationContainerViewModelTest
Flag: EXEMPT bugfix
Change-Id: Ieaa8d1d6ca380fbd0fdb6552b087215208953974