extmod/modlwip: Fix case where concurrency lock isn't released on error.
extmod/modlwip: Fix case where concurrency lock isn't released on error.

MrSurly/micropython,pozetroninc/micropython,pramasoul/micropython,adafruit/circuitpython,selste/micropython,trezor/micropython,pramasoul/micropython,henriknelson/micropython,bvernoux/micropython,bvernoux/micropython,pfalcon/micropython,tobbad/micropython,bvernoux/micropython,trezor/micropython,pramasoul/micropython,henriknelson/micropython,kerneltask/micropython,selste/micropython,selste/micropython,pfalcon/micropython,henriknelson/micropython,selste/micropython,tobbad/micropython,tobbad/micropython,kerneltask/micropython,trezor/micropython,adafruit/circuitpython,pozetroninc/micropython,tobbad/micropython,pramasoul/micropython,kerneltask/micropython,MrSurly/micropython,trezor/micropython,adafruit/circuitpython,trezor/micropython,henriknelson/micropython,bvernoux/micropython,selste/micropython,henriknelson/micropython,MrSurly/micropython,pfalcon/micropython,kerneltask/micropython,bvernoux/micropython,pfalcon/micropython,kerneltask/micropython,pozetroninc/micropython,adafruit/circuitpython,pfalcon/micropython,pozetroninc/micropython,adafruit/circuitpython,pozetroninc/micropython,adafruit/circuitpython,MrSurly/micropython,pramasoul/micropython,tobbad/micropython,MrSurly/micropython