CameraService: Initialize two fields in constructor

isIndividual was potentially being read uninitialized in
onSensorPrivacyChanged().  In theory, userId wasn't being read
uninitialized with the current logic, but we choose to
future-proof by initializing it to a known value.

Bug: 170156750
Bug: 162549680
Test: TreeHugger
Change-Id: I7672fe90556ab71bc3d9021d5adc91b9f4e0a5c3