status/network: Sync active connections again on connection-added
NetworkManagers NmClient has a bug for wireguard connections where the
notify::active-connections and connection-added are emitted in the wrong order:
When a wireguard connection gets activated, notify::active-connections is
emitted first, then connection-added happens.
We currently expect these signals to emitted in the correct order, so our VPN
toggle is not actually updated when a wireguard connection is established.
Until this bug is fixed in NetworkManager, work it around by calling
_syncActiveConnections() manually after we see ::connection-added.