Use the new algorthm preferentially when getting external IP

src/calibre/utils/mdns.py

@@ -89,6 +89,10 @@ _ext_ip = None
 def get_external_ip():
     global _ext_ip
     if _ext_ip is None:
+        from calibre.utils.ip_routing import get_default_route_src_address
+        try:
+            _ext_ip = get_default_route_src_address()
+        except Exception:
             _ext_ip = _get_external_ip()
     return _ext_ip