healthd: Adds fake battery properties for devices with no battery.

Devices which have no battery and are always plugged in will not have
any battery property initialized. This causes the 'stable power' to
never be switched which is required for updating apps.

This change recognizes such a device and manually sets the battery to
100% and charger status to connected to AC mains. It will also fake the
battery temperature.

Bug: 24258855
Change-Id: I98e5ed0dbeb7f2ab6d3802cd7e0f3a269bd8f31f
Signed-off-by: Ruchi Kandoi <kandoiruchi@google.com>