Add enable-timestamps to default babel config

When the babel config code was recently updated enable-timestamps was
removed from the default argument set for new interfaces by accident
resulting in latency reporting being broken in networks running newer
versions of Rita. This patch resolves that issue

babel_monitor/src/lib.rs

@@ -274,6 +274,7 @@ fn build_interface_config_string(config: BabeldInterfaceConfig) -> String {
     command.push_str(&format!("rtt-max {} ", config.rtt_max));
     command.push_str(&format!("hello-interval {} ", config.hello_interval));
     command.push_str(&format!("update-interval {} ", config.update_interval));
+    command.push_str("enable-timestamps true");
     command
 }