[Port from 2.0] Fixed authentication issue for non-REGISTER requests

Thanks to Stefan Sayer for this out!

etc/ser-oob.cfg

@@ -885,11 +885,10 @@ route[AUTHENTICATION]
 	}
 
 	# check if the UID from the authentication matches the From header
-	$authuid = $uid;
-	if (!lookup_user("$fu.uid", "@from.uri")) {
+	if (!lookup_user("$fr.uid", "@from.uri")) {
 		del_attr("$uid");
 	}
-	if ($fu.uid != $fr.authuid) {
+	if ($fu.uid != $fr.uid) {
 		sl_reply("403", "Fake Identity");
 		drop;
 	}