pytests: Add test for audio output

this brings over the audio test from !51 (closed) but the test failes on

kernel: Linux pureos 5.3.0-rc2-g24e3d989d #1 SMP PREEMPT Fri Aug 2 11:09:12 PDT 2019 aarch64 GNU/Linux

also if i run the command by hand:

$ alsabat -D plughw:CARD=sgtl5000,DEV=0 -c2 --saveplay /tmp/default_dual.wav --standalone           
alsa-utils version 1.1.8


Return value is -2