Correctly detect "Wi-Fi disabled" state and use more appropriate icon

Two commits, don't squash:

Use more appropriate wired and wireless disconnection icons

The logic in ConnectionIcon::setDisconnectedIcon() eventually returns
icons that end with  -available instead of -disconnected. This
contradicts the function name and is incoherently different from what
the notification shows.

Instead, return icons ending in -disconnected.

.

Correctly detect "Wi-Fi disabled" state in connection icon

Previously the Wi-Fi-specific code here was skipped when you disable
Wi-Fi, and fell through to the generic case which shows a wired icon.

There's no reason to be this restrictive; don't be, so the "Wi-Fi
disabled" case is handled properly.`

Before	After