Resolve mDNS not restarting on wifi dn/up

also changed log prefix for mDNS  from DNS: to mDN:

tasmota/i18n.h

@@ -680,7 +680,7 @@
 #define D_LOG_KNX "KNX: "
 #define D_LOG_LOG "LOG: "          // Logging
 #define D_LOG_MODULE "MOD: "       // Module
-#define D_LOG_MDNS "DNS: "         // mDNS
+#define D_LOG_MDNS "mDN: "         // mDNS
 #define D_LOG_MQTT "MQT: "         // MQTT
 #define D_LOG_OTHER "OTH: "        // Other
 #define D_LOG_RESULT "RSL: "       // Result

tasmota/support_network.ino

@@ -36,6 +36,7 @@ void StartMdns(void) {
 //        mdns_delayed_start--;
 //      } else {
 //        mdns_delayed_start = Settings.param[P_MDNS_DELAYED_START];
+        MDNS.end(); // close existing or MDNS.begin will fail
         Mdns.begun = (uint8_t)MDNS.begin(TasmotaGlobal.hostname);
         AddLog_P(LOG_LEVEL_INFO, PSTR(D_LOG_MDNS "%s"), (Mdns.begun) ? D_INITIALIZED : D_FAILED);
 //      }