wrap: Set PulseAudio as the default ALSA driver if available
To avoid audio issues, if we have successfully binded a PulseAudio socket, we should also set it as the default driver in ALSA.
Addresses: #65 (closed) Partially addresses: https://github.com/ValveSoftware/steam-runtime/issues/371
Signed-off-by: Ludovico de Nittis ludovico.denittis@collabora.com