mod_s2s: fixes #533...

Throwing error() within s2s code will propagate badly within the server backend causing the socket to linger unhandled and Metronome to crash, we shall properly handle and the exception and not interrupt code execution.

plugins/mod_s2s/mod_s2s.lua

@@ -367,7 +367,11 @@ function stream_callbacks.streamopened(session, attr)
 		end
 	elseif session.direction == "outgoing" then
 		-- If we are just using the connection for verifying dialback keys, we won't try and auth it
-		if not attr.id then error("stream response did not give us a streamid!!!"); end
+		if not attr.id then
+			log("error", "stream response did not give us a streamid!");
+			session:close({ condition = "undefined-condition", text = "ID on the stream response is missing" });
+			return;
+		end
 		session.streamid = attr.id;
 
 		-- If server is pre-1.0, don't wait for features, just do dialback