healthd: don't report fake data for battery-less devices

If the kernel does not implement a power_supply class device of type
battery, do not report fake data, instead report the following by
default:

* batteryPresent = false (instead of true),
* charging status = unknown (instead of charging),
* capacity = 0 (instead of 100%),
* health = unknown (instead of good),
* AC charger online not modified (instead of forcing true)

If no charger and no battery devices are supplied by the kernel, the
AC charger online property will no longer be forced to true.  Devices
that are always plugged into AC power should either implement a
power_supply class charger device or implement a Health HAL that sets
properties appropriately.

Bug: 34507420
Test: manual: gce_x6_phone (no battery or charger),
      boots and stays booted, inspect properties
Merged-In: I14cb3b685e8130428e417e7d08c4246f7415210a

Change-Id: I64bd4431af10f3d232f36fcf8d356b6d88b08013