mod_c2s: Make c2s_timeout timer reachable to allow access from other modules

E.g. the timeout could be extended under certain conditions.

plugins/mod_c2s.lua

@@ -369,10 +369,12 @@ function listener.onconnect(conn)
 	end
 
 	if c2s_timeout < math.huge then
-		add_task(c2s_timeout, function ()
+		session.c2s_timeout = add_task(c2s_timeout, function ()
 			if session.type == "c2s_unauthed" then
 				(session.log or log)("debug", "Connection still not authenticated after c2s_timeout=%gs, closing it", c2s_timeout);
 				session:close("connection-timeout");
+			else
+				session.c2s_timeout = nil;
 			end
 		end);
 	end