PadMessageHandler: Rename createSessionInfo to createSessionInfoAuth
PadMessageHandler: Rename createSessionInfo to createSessionInfoAuth

The function doesn't create the session info -- it creates the auth
property of existing session info.

ether/etherpad-lite,storytouch/etherpad-lite,storytouch/etherpad-lite,ether/etherpad-lite,storytouch/etherpad-lite,ether/etherpad-lite