Fix race conditions in creation of Frame Relay Switch

gns3server/compute/dynamips/nodes/frame_relay_switch.py

@@ -239,10 +239,10 @@ class FrameRelaySwitch(Device):
         """
 
         if port1 not in self._nios:
-            raise DynamipsError("Port {} is not allocated".format(port1))
+            return
 
         if port2 not in self._nios:
-            raise DynamipsError("Port {} is not allocated".format(port2))
+            return
 
         nio1 = self._nios[port1]
         nio2 = self._nios[port2]