-added 2 more DUM PRACK tests to TFM DUM
-modified ServerInviteSession so that we change state before calling callbacks - this means
 moving the calling of onPrack from handlePrack to the appropriate state fns 



git-svn-id: https://svn.resiprocate.org/rep/resiprocate/branches/b-uasprack-20130904@10645 ddefafc4-47db-0310-ae44-fa13212b10f2