Mininet-WiFi: handover supported by bgscan (Background scanning) and wmediumd HD

Content of sta1.staconf ctrl_interface=/var/run/wpa_supplicant network={ ssid="handover" psk="123456789a" scan_freq=2412 key_mgmt=WPA-PSK proto=WPA2 pairwise=CCMP bgscan="simple:10:-45:20" }