Fix fingerprint unlock stuck after renaming

FingerprintAuthenticationClient wasn't cancelled successfully because cancelletion signal was set to null.

Test: Manual - rename an existing fingerprint and observe fingerprint unlock can be entered again
Test: atest FingerprintSettingsFragmentTest

Fixes: 283926104
Change-Id: Id33cc3d3e8052f5cc39eddac26a75047d3139633
2 files changed