chat: use contact-chat-state-changed signal
chat: use contact-chat-state-changed signal

Now that we have a signal giving us a prepared TpContact there is no need to
use the empathy variant as we can easily create the EmpathyContact directly.

https://bugzilla.gnome.org/show_bug.cgi?id=675807

Distrotech/telepathy-account-widgets,GNOME/telepathy-account-widgets,GNOME/telepathy-account-widgets,GNOME/telepathy-account-widgets,Distrotech/telepathy-account-widgets