Fixed processing artifical notifications in session

Ignore-this: 8d7cf08dd58bae521337fcfe24534c7b

darcs-hash:20130204145844-56b4d-ddf3e355bef1c11e1355ed4972724a225972c640
Avoid sending adding participant progress if the answer is final

Ignore-this: bda34fb0bf4a89713a7d79a21109c15f

darcs-hash:20130201121502-56b4d-2a0f684b6ab4a68f360e3d1b1b26a0a75bd63ce9