The Linux kernel supports reporting "cold" battery health to sysfs.
Android framework has not implemented this and it defaults to "unknown"
This adds handling the cold battery health.
Change-Id: Idcc156aae6aabce73391081143f79d052edf332e
If the battery files can't be found return status_unkown instead of an
error. On systems where we haven't brought up battery stats yet they
assume the battery is dead and turn off as soon as the runtime starts
Signed-off-by: Rebecca Schultz Zavin <rebecca@android.com>