Hide DeviceEntryIcon on alternateBouncer => dreaming transition

So that the UDFPS view appropriately updates and doesn't attempt
to authenticate fingerprint on subsequent transitions.

Test: atest AlternateBouncerToDreamingTransitionViewModelTest
Test: enroll UDFPS; enable screen saver; go to lockscreen and
tap on an affordance to bring up the alternate bouncer;
press power button to dream; double press power button to camera;
observe fingerprint is not possible
Fixes: 440629582
Flag: EXEMPT bugfix

Change-Id: Ib6b641738753afa38c791af76780fe813612db03