test: realtek net config default  to none
test: realtek net config default  to none

Changing this to none as result of build failures. Wifi needs own configuration
per an enviroment. By setting this to none, net tests are skipped for Realtek
platform.

infinnovation/mbed-os,karsev/mbed-os,andcor02/mbed-os,c1728p9/mbed-os,infinnovation/mbed-os,Archcady/mbed-os,c1728p9/mbed-os,kjbracey-arm/mbed,infinnovation/mbed-os,betzw/mbed-os,ryankurte/mbed-os,CalSol/mbed,infinnovation/mbed-os,betzw/mbed-os,ryankurte/mbed-os,c1728p9/mbed-os,karsev/mbed-os,Archcady/mbed-os,betzw/mbed-os,mbedmicro/mbed,mazimkhan/mbed-os,c1728p9/mbed-os,ryankurte/mbed-os,Archcady/mbed-os,karsev/mbed-os,kjbracey-arm/mbed,CalSol/mbed,andcor02/mbed-os,karsev/mbed-os,ryankurte/mbed-os,mbedmicro/mbed,betzw/mbed-os,Archcady/mbed-os,andcor02/mbed-os,karsev/mbed-os,mbedmicro/mbed,andcor02/mbed-os,CalSol/mbed,andcor02/mbed-os,infinnovation/mbed-os,mbedmicro/mbed,ryankurte/mbed-os,ryankurte/mbed-os,betzw/mbed-os,mbedmicro/mbed,kjbracey-arm/mbed,c1728p9/mbed-os,mazimkhan/mbed-os,karsev/mbed-os,infinnovation/mbed-os,mazimkhan/mbed-os,mazimkhan/mbed-os,c1728p9/mbed-os,mazimkhan/mbed-os,mazimkhan/mbed-os,Archcady/mbed-os,kjbracey-arm/mbed,andcor02/mbed-os,Archcady/mbed-os,CalSol/mbed,CalSol/mbed,CalSol/mbed,betzw/mbed-os