audio: Do not prevent pulseaudio from autospawning a server.

This prevents downgrading the audio experience to ALSA on system
running a vanilla pulseaudio configuration that relies on pulseaudio
being able to manage the pulseaudio server itself.

* src/media/audio/pulseaudio/pulselayer.cpp (PulseLayer::PulseLayer)
[PA_CONTEXT_NOAUTOSPAWN]: Replace flags argument value with
PA_CONTEXT_NOFLAGS.
* src/media/audio/pulseaudio/pulselayer.h: Fix typo.

GitLab: #473
Change-Id: I219223dd8a1237a51b3e5bf60d6535518d748b63