Cancel current animation instead of candidate

Otherwise everything along the way confidently ignores this
and Keyguard doesn't even see the timeout and force-abort
coming when it hits. This leaves an animation timer running
for 950ms which sets occlude status on finish callback and
causes unpleasant race conditions.

Change-Id: I7b3dcd06e7483fde745a1d56dfee7c4efc262ed7
Test: atest android.server.wm.KeyguardTests
Test: specific case to be added in b/274003805
Bug: 275650364