Reset dismissAction and notifyCancel dismissCallbacks when altBouncer removed

Fixes: 351712715
Flag: EXEMPT bugfix
Test: atest AlternateBouncerViewModelTest
Test: Enroll SFPS or UDFPS; tap on smartspace on the lockscreen;
observe alternate bouncer; press power button to screen off;
press power button to screen on and then authenticate with FP;
observe device enters and does NOT trigger the smartspace intent
that should have been cancelled after the power off

Change-Id: I110eb99219d806ac901d56199ad30ca0b221bdc4