Skip cursor loader if not needed

The cursor loader was being started when the battery prediction
feature was not enabled. This could lead to null pointers because
it was not possible to provide it with a valid URI which would
make the CursorLoader unhappy. This CL makes it so we just skip
the CursorLoader initialization entirely when we know the feature
is disabled so we don't have this issue. It also includes a test
to make sure this does not regress.

Test: Robotests
Bug: 38371686
Change-Id: I4f6f6278bbc16668bca0b51fcc7e30f27a9e216f