Make sure that the unmuter runs after the sound card is available.

Per email discussion with Tom Gundersen regarding
espeakup.service.  livecd-sound-unmuter basically needs
to do the same thing as espeakup.
Remove espeakup systemd files.

The files from the ArchLinux package will work fine now.
Incorporate all changes from Archiso.

Copied wholesale from archiso's configs/releng.  Sorry again for losing
credits with these dumps.