Initialize field in constructor

Rather than risk a poorly written future test failing to call
setOverrideCameraDisabled() prior to isCameraDisabled() being
called, we just make sure sure this field has a consistently
set value.  This will help protect against a "flaky" future
test that would have been using uninitialized memory.

Test: TreeHugger
Change-Id: Ie6d9bb7df25786d2c5f6064d897949ffccbe6e72