status/network: Always notify icon-name on strength change

We do want to update the best AP on strength change, in case we can switch to a better one.

But even if we can't and the API is unchanged, the icon should be updated to reflect the change.

This will be more important with !2407 (merged)/!2408 (merged) where the signal is used to resort the list of wifi networks in the quick settings menu. We don't want to base that on a strength a network used to have hours ago 😉