esp8266/modnetwork: Make sure to intern string passed to .config("param").
esp8266/modnetwork: Make sure to intern string passed to .config("param").

This is the proper fix for
https://github.com/micropython/micropython/issues/3442.

tralamazza/micropython,pramasoul/micropython,adafruit/circuitpython,trezor/micropython,tralamazza/micropython,henriknelson/micropython,infinnovation/micropython,blazewicz/micropython,bvernoux/micropython,ryannathans/micropython,pramasoul/micropython,blazewicz/micropython,adafruit/micropython,kerneltask/micropython,blazewicz/micropython,adafruit/micropython,pozetroninc/micropython,pozetroninc/micropython,bvernoux/micropython,adafruit/micropython,selste/micropython,dmazzella/micropython,selste/micropython,MrSurly/micropython,pfalcon/micropython,trezor/micropython,pozetroninc/micropython,MrSurly/micropython,dmazzella/micropython,pramasoul/micropython,infinnovation/micropython,MrSurly/micropython,swegener/micropython,swegener/micropython,ryannathans/micropython,MrSurly/micropython,adafruit/circuitpython,henriknelson/micropython,swegener/micropython,pozetroninc/micropython,henriknelson/micropython,infinnovation/micropython,infinnovation/micropython,bvernoux/micropython,selste/micropython,blazewicz/micropython,adafruit/circuitpython,pfalcon/micropython,tobbad/micropython,trezor/micropython,kerneltask/micropython,tobbad/micropython,pfalcon/micropython,ryannathans/micropython,kerneltask/micropython,swegener/micropython,MrSurly/micropython,henriknelson/micropython,dmazzella/micropython,pozetroninc/micropython,trezor/micropython,trezor/micropython,adafruit/circuitpython,tobbad/micropython,kerneltask/micropython,pramasoul/micropython,kerneltask/micropython,adafruit/micropython,adafruit/circuitpython,infinnovation/micropython,blazewicz/micropython,adafruit/micropython,selste/micropython,bvernoux/micropython,pfalcon/micropython,ryannathans/micropython,swegener/micropython,tobbad/micropython,tobbad/micropython,tralamazza/micropython,selste/micropython,bvernoux/micropython,pramasoul/micropython,pfalcon/micropython,adafruit/circuitpython,dmazzella/micropython,tralamazza/micropython,ryannathans/micropython,henriknelson/micropython