fix: wifi interfaces do not always get deconfigured correctly

[pony1k]

Fixes #1222.

[a-gave]

Thanks. Tested and seems fine. I would merge this.

Testing commands with applied the patch

# Adding the ieee80211s modes to the 2ghz wifi mode list
root@gemtek-wvrtm-130acn:~# uci add_list lime-node.2ghz.modes='ieee80211s'; uci commit lime-node; lime-config
# iwinfo show only 1 interface
root@gemtek-wvrtm-130acn:~# iwinfo  | grep LiMe
wlan1-mesh ESSID: "LiMe"
# But /etc/config/wireless was modified
root@gemtek-wvrtm-130acn:~# uci show wireless | grep "\-mesh"
wireless.lm_wlan0_mesh_radio0.ifname='wlan0-mesh'
wireless.lm_wlan1_mesh_radio1.ifname='wlan1-mesh'
# running 'wifi' is still needed to apply new configurations
root@gemtek-wvrtm-130acn:~# wifi
# now wlan0-mesh interface is created
root@gemtek-wvrtm-130acn:~# iwinfo  | grep LiMe
wlan0-mesh ESSID: "LiMe"
wlan1-mesh ESSID: "LiMe"
#
#
# Removing ieee80211s
root@gemtek-wvrtm-130acn:~# uci del_list lime-node.2ghz.modes='ieee80211s'; uci commit lime-node; lime-config
# interface is removed from /etc/config/wireless, 
root@gemtek-wvrtm-130acn:~# uci show wireless | grep "\-mesh"
wireless.lm_wlan1_mesh_radio1.ifname='wlan1-mesh'
# wifi is still required to apply
# else the interface is still present in 'iwinfo', 'ls /sys/class/net' and via 'ip link'
root@gemtek-wvrtm-130acn:~# iwinfo | grep mesh
wlan0-mesh ESSID: "LiMe"
wlan1-mesh ESSID: "LiMe"
root@gemtek-wvrtm-130acn:~# wifi
root@gemtek-wvrtm-130acn:~# iwinfo | grep mesh
wlan1-mesh ESSID: "LiMe"