[BiometricsV2] Fix fingerprint add another fail

Fix enrolling can't finished because FingerprintEnrollment attaches to
wrong ViewModel during onCreate() with non-null savedInstance after
rotation.

Read latest fragment through findFragmentById to fix it

Bug: 275513362
Test: atest FingerprintEnrollmentActivityTest
Change-Id: Icb2c0edec325a813ec5a7822aba39ca201d2d8e9