config: disable promiscuous mode by default

Author: AlaiaL

apps/units/flexible_du/split_7_2/ru_ofh_config.h

@@ -81,7 +81,7 @@ struct ru_ofh_unit_cell_config {
   /// Ethernet network interface name or identifier.
   std::string network_interface = "enp1s0f0";
   /// Promiscuous mode flag.
-  bool enable_promiscuous_mode = true;
+  bool enable_promiscuous_mode = false;
   /// MTU size.
   units::bytes mtu_size{9000};
   /// Radio Unit MAC address.