travis: Exclude some uasyncio tests on OSX.
travis: Exclude some uasyncio tests on OSX.

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