Avoid sending warning message all the time for Ethernet switch.

gns3server/compute/dynamips/nodes/ethernet_switch.py

@@ -132,6 +132,7 @@ class EthernetSwitch(Device):
     @console_type.setter
     def console_type(self, console_type):
 
+        if self._console_type != console_type:
             if console_type == "telnet":
                 self.project.emit("log.warning", {
                     "message": '"{name}": Telnet access for switches is not available in this version of GNS3'.format(name=self._name)})