There might not be udev notification about every battery capacity
percent value change. While this is usually harmless when battery
is sufficiently full, it can cause issues like missed battery low
notifications and/or delay battery empty shutdown so much that
battery gets too depleted for regular bootup.

Poll power supply device properties in process watchdog heartbeat
pace i.e. about every 36 seconds of uptime not spent in suspend.

Periodic udev polling is enabled by default, but can be disabled
via mce configuration.
Signed-off-by: Simo Piiroinen <simo.piiroinen@jollamobile.com>