Also pull the Allow headers (previous behavior)

lib/msf/core/exploit/sip.rb

@@ -7,7 +7,7 @@ module Msf
   module Exploit::Remote::SIP
     # Parses +response+, extracts useful metdata and then reports on it.
     # Returns true iff the response was a valid SIP response
-    def parse_response(response, rhost, proto, desired_headers = %w(User-Agent Server))
+    def parse_response(response, rhost, proto, desired_headers = %w(User-Agent Server Allow))
       endpoint = "#{rhost}:#{rport}/#{proto}"
       begin
         options_response = Rex::Proto::SIP::Response.parse(response)