No Name

In some cases, I need the ethernet cable and WiFi :
- first time to set up the WiFi and test it.
In some other cases, I need only the ethernet cable :
- to have a better stable network cnx.
And in some other cases, I need only the WiFi cnx :
- I don't want to link the opi with a very long cable.
- The opi should be mobile and need to be "stored" it in some particulary places. 
 
This time, the main problem is not that I have only a WiFi lost when disconnecting the ethernet cable but I can't have any WiFi cnx if the ethernet cable is not plugged. It means that if I start the device without the ethernet cable plugged, I don't have any WiFi cnx. So I can't use the opi in "WiFi only mode". And I have found after about one week of research that the problem seems to appear with my last WiFi Access Point device (that I'm using every day for about 4-6 months from now).
 
I have found this article that I have tried to follow without any success (probably because I have used the Network Manager and the IfUpDown with WiFi together). This is a workaround to manage only the ethernet plug/unplug (not the "only Wifi" case)