Fix headless startup of the GNS3 VM

gns3server/controller/gns3vm/__init__.py

@@ -267,6 +267,7 @@ class GNS3VM:
             engine.vmname = self._settings["vmname"]
             engine.ram = self._settings["ram"]
             engine.vpcus = self._settings["vcpus"]
+            engine.headless = self._settings["headless"]
             compute = yield from self._controller.add_compute(compute_id="vm",
                                                               name="GNS3 VM is starting ({})".format(engine.vmname),
                                                               host=None,