Fix embedded multicast examples

[sashacmc]

At the moment, in most of the embedded examples (e.g. espidf, arduino), multicast mode is set incorrectly, if you simply change the defines to peer/multicast, the peer mode will be set, but the CONNECT string will still go as a connection endpoint, but it should be as a listening endpoint (see e.g. unix, rpi_pico examples)

[vortex314]

Indeed, burned myself also on this one. The ZENOH_DBUG and debug level tracing helped to address this.

#define CLIENT_OR_PEER 0 // 0: Client mode; 1: Peer mode
#if CLIENT_OR_PEER == 0
#define MODE "client"
#define CONNECT "" // If empty, it will scout
#elif CLIENT_OR_PEER == 1
#define MODE "peer"
#define CONNECT "udp/224.0.0.123:7447#iface=lo" 
#endif

  if (strcmp(CONNECT, "") != 0) {
    //        zp_config_insert(z_loan_mut(config), Z_CONFIG_CONNECT_KEY,
    //        CONNECT);
    zp_config_insert(z_loan_mut(config), Z_CONFIG_LISTEN_KEY, CONNECT);
  }