Add option path rate tx/rx

These two options are mandatory since dynamic shapping
is disabled for now.

Signed-off-by: Adrien Gallouët <adrien@gallouet.fr>

src/ctl.h

@@ -23,6 +23,8 @@ struct ctl_msg {
         struct {
             struct sockaddr_storage addr;
             enum mud_state state;
+            unsigned long rate_tx;
+            unsigned long rate_rx;
         } path;
         struct mud_path path_status;
         struct {