Fix 'EthernetSwitch' object has no attribute 'hw_virtualization'

Fix #828

gns3server/compute/dynamips/nodes/bridge.py

@@ -106,3 +106,6 @@ class Bridge(Device):
 
         yield from self._hypervisor.send('nio_bridge remove_nio "{name}" {nio}'.format(name=self._name, nio=nio))
         self._nios.remove(nio)
+
+    def hw_virtualization(self):
+        return False

gns3server/compute/dynamips/nodes/device.py

@@ -108,3 +108,6 @@ class Device:
         """
 
         raise NotImplementedError
+
+    def hw_virtualization(self):
+        return False