Make wireless toggle more predictable

[devgianlu]

1. Stop relying on /sys/class/net/wlan0/flags == 0x1003
   • Checking the content of the file with an hardcoded value is generally bad
   • If the value changes the WiFi would be marked down even if the UP bit is still set (e.g. 0x1003 vs 0x1103)
   • With "single network mode" enabled the toggle remains stuck on "off" when a wired connection is available
   • If there is need to communicate that the WiFi will not be used when a cable is connected, we should do it in some other way
2. Fix race-condition between v-conf save and wireless.js
   • v-conf saves async, making race conditions very common
   • When wireless settings are saved, the wireless SystemD service is restarted
   • The wireless.js script was reading the config directly before it was saved

These changes are temporary merged on feat/acert.