* sip_util.c: fix 484 respose to REFER in sip_response_terminates_dialog()

  Asterisk (v 1.2.7.1) does response with 484 if a client does send a refer
  with a @ReferTo header to an unknown number.  This is therefore not
  fundamentally wrong and the dialog should not be destroyed!



git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@11829 d0543943-73ff-0310-b7d9-9358b9ac24b2