pulse: fail if the server is Pipewire

Some distributions allow installing both Pipewire and PulseAudio, leaving Pipewire to manage only video devices.

On one hand, if we leave the Pipewire output with higher priority, then we do not get access to any audio output device in this case. On the other hand, if we simply probe the PulseAudio output first, then we will never use the native Pipewire protocol, even if the PulseAudio service is not actually running, since Pipewire emulates PulseAudio.

So this checks the name of the PulseAudio daemon, and uses the PulseAudio protocol if and only if the server is not Pipewire.