Set empathy's media role to phone for so pulse can do policy on it

Set empathy's media role to phone for so pulse can do policy on it

Empathy's media role should be phone. Apart from voip calls the only sounds we
make are event sounds via libcanberra, which correctly sets the role to event
when playing a sound. For more information see:
  http://pulseaudio.org/wiki/ApplicationProperties

From: Sjoerd Simons <sjoerd.simons@collabora.co.uk>

svn path=/trunk/; revision=2634