fix empty reply from server error (espressif#2903)

The flush causes an empty response a client side. see espressif#2902

Author: pmalhaire

libraries/ESPmDNS/examples/mDNS_Web_Server/mDNS_Web_Server.ino

@@ -96,7 +96,6 @@ void loop(void)
  req = req.substring(addr_start + 1, addr_end);
  Serial.print("Request: ");
  Serial.println(req);
- client.flush();
 
  String s;
  if (req == "/")
@@ -115,6 +114,7 @@ void loop(void)
  }
  client.print(s);
 
+ client.stop();
  Serial.println("Done with client");
 }