Reset canHandleTouches to false when udfpsViewIsDetached

Fixes: 338860324
Flag: com.android.systemui.device_entry_udfps_refactor
Test: manually trigger camera from various keyguard states;
observe fingerprint is not triggered when the keyguard
is occluded

Change-Id: I34a2cbcd2e2cc47ce5043227b6595246431b526f