don't take session lock in astman_send_error() and astman_send_response(),...

don't take session lock in astman_send_error() and astman_send_response(), since it is no longer needed
don't build authority string and event string for every session in manager_event(), do it only once


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@6704 65c4cc65-6c06-0410-ace0-fbb531ad65f3