NetworkManager should roam (aggressively) if there is mulitple APs
NetworkManager currently only set a short scan interval if the network is
WPA Enterprise or Dynamic WEP.
WPA-PSK networks with multiple APs is a thing, so we should probably handle it better. I'm not sure what the best way to implement it is, maybe we could look at
seen-bssids and if count > 1 switch to a short scan interval.