Audio Unit initialization fix on macOS

[daft-panda]

The current Audio Unit initialization logic produces errors when trying to use output devices as input Audio Units. This results in only some output devices being present when enumerating the host devices.

[ahcm]

This fixes the error:
Error getting supported output configs: BackendSpecific { err: BackendSpecificError { description: "Invalid property value" } }

Find attached output from the example enumerate, with and without the patch.
Please merge.

Best
Andreas

cpal_enumerate_default_N9_daft-panda.txt
cpal_enumerate_default_N9.txt
cpal_enumerate_default_speaker_daft-panda.txt
cpal_enumerate_default_speakers.txt

[mdwn]

This looks to me to be a pretty benign one-liner change -- I'd love to get this merged. @abique, @est31, would it be possible to get this merged?

[etsuko-io]

I applied this change in my local fork and it fixes an issue that I've been experiencing with output devices not being listed. When merged I expect it would close #814 and by extension #905.

[will3942]

This fixes a long standing issue on MacOS - It would be great if we can get this merged @est31

[spennythug]

I can confirm that this fixes the issues already mentioned for me

I have also been experiencing an issue where I can only use certain output devices if they are also selected as the system's output device. By applying this same change in the default_config function, (around line 400) this issue is fixed for me as well. I assume this only happens when using default_output_config

I'd be happy to put in a separate PR, if that's necessary, but it seems like this change could simply be tacked on to this one