Hi Guix,

After looking at my older patch (which no longer cleanly applies), I've
noticed, that pulseaudio doesn't even read the files from /etc.  This
is troublesome in multiple ways.  For one, pulseaudio causes >500
rebuilds (with >900 dependent packages) and is therefore staging
material, for the other, hardcoding /etc in such a way breaks
pulseaudio without the service.

So far, I've only tested containers via `guix environment --container`, 
but from what I can gather with strace, the config file is indeed read
and hence flat-volumes are eliminated.  Other ways of making pulseaudio
accept /etc are very welcome.  Looking at Nix, they configure
pulseaudio with "--sysconfdir=/etc", but then override sysconfdir and
pulseconfdir during install.  I'm not quite sure which solution is
"better", but neither is going to read the config shipped with the
package.

Note: before this can be applied on staging,
a66ee82a05d8ff1ef7c5ff9ac7723cb32fc4e22a needs to be applied.

Regards,
Leo