Update getAuthenticatorId logic

1) Theoretically, 0 is a valid random authenticatorId
2) A more precise way of handling this is by checking enrollment
   status. If the sensor has no enrollments, do not add its
   authenticatorId to the list

Bug: 183142128
Test: atest CtsBiometricsTestCases
Change-Id: I80e9b27a297480b02015b20788d56703833245ab