[upower] update property only if different

upowers signal changed does not give a hint which property is changed :(
So, all properties should be read (!!!) and compared to previous values

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>
[ofono] provider

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>