Verify ATMS state only with the old keyguard handling

The new keyguard transition will go through transitions and will not
directly call into the ATMS to trigger a keyguard change. Verify the
ATMS state only when the corresponding flag is disabled.

In the same test class, multiple tests exist for the new keyguard
transition requires the flag to be enabled.

Bug: 364930619
Test: WindowManagerLockscreenVisibilityManagerTest
Flag: com.android.window.flags.ensure_keyguard_does_transition_starting
Change-Id: Iae40452a3a50dc91f67cf2e675a21874fe4f6835