parselogs.py: ignore pulseaudio startup warning messages

parselogs.py: ignore pulseaudio startup warning messages

If set default syslog to rsyslog, we can see below messages
in user.log,

[pulseaudio] authkey.c: Failed to open cookie file
[pulseaudio] authkey.c: Failed to load authentication key

They are only warnings when cookie file is not found. And
PulseAudio will create it if it doesn't exist.

refer:
https://wiki.archlinux.org/index.php/PulseAudio/Configuration
https://lists.freedesktop.org/archives/pulseaudio-discuss/2014-December/022719.html

Signed-off-by: Changqing Li <changqing.li@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Steve Sakoman <steve@sakoman.com>