It seems UPower sets the "Is Present" property to false for newly added devices that have

not yet been probed. This is a contradiction to the specs that say this property is invalid
for non-primary batteries (such as mice).
Now also taking that into account for non-power-supply-batteries. Have to see if that causes
regressions for other devices. At least my Trackball works better now ;)
CCBUG: 320678