typo fix in sip_im_session2.py

darcs-hash:20090313083708-b2873-311f43f55b6948546b848f9991c2efc894cdd924
fix display_name in config was ignored

darcs-hash:20090313112827-b2873-a40838019e1329971b10c5aed546925da4d3fd3d