This fixes the case when Jack Audio Daemon is running
as a service via `services.jack.jackd` and Pulseaudio
running as a *user* service.
Two issues prevented connecting `pulse` with `jackd`:
* Missing `JACK_PROMISCUOUS_SERVER` environment variable for `pulse` user service,
resulting in `pulse` trying to access `jackd` as if it was running as part of
the users session.
* `jackd` not being able to access socket created by `pulse` due to socket
created using user ID and `users` group. Change allows `jackd` to access
the socket created by `pulse` correctly.
`pulse` now also autoloads `module-jack-sink` and `module-jack-source`
if `services.jack.jackd.enable` is set.
The default `pulse` package is now set to `pulseaudioFull` automatically
if `services.jack.jackd.enable` is set.
