sip_im_session: minor fix

darcs-hash:20090129074832-b2873-6d8592a52d8d2b5a6c18996f9ba05e562858e82f
sip_im_session: removed "Log opened"/ "Log closed" messages

darcs-hash:20090129075422-b2873-7f0b6c05c195399dcf384821b8d597f6c099c92e