Prevent corruption of VM in VirtualBox when using linked clone

Fix https://github.com/GNS3/gns3-gui/issues/1821

gns3server/handlers/api/compute/virtualbox_handler.py

@@ -112,10 +112,13 @@ class VirtualBoxHandler:
         vbox_manager = VirtualBox.instance()
         vm = vbox_manager.get_node(request.match_info["node_id"], project_id=request.match_info["project_id"])
 
-        if "vmname" in request.json:
-            vmname = request.json.pop("vmname")
-            if vmname != vm.vmname:
-                yield from vm.set_vmname(vmname)
+        if "name" in request.json:
+            name = request.json.pop("name")
+            vmname = request.json.pop("vmname", None)
+            if name != vm.name:
+                vm.name = name
+                if vm.linked_clone:
+                    yield from vm.set_vmname(vm.name)
 
         if "adapters" in request.json:
             adapters = int(request.json.pop("adapters"))