Add the ability to end pulsing immediately

If a HUN is immediately cancelled after posting,
make sure the Doze pulsing state can correctly exit
so that the device isn't stuck pulsing in screen on.

Test: manually (hardcode) a notification to immediately stop
pulsing after its been requested to pulse. observe that AoD
eventually exits the pulsing state.
Test: atest DozeTriggersTest DozeServiceHostTest
Fixes: 221601821

Change-Id: Ibf349f97edbb54a9eb36eb4d33175867d7cf7b13