Refactor aux port allocation

This move the allocation of aux port to the base vm.
Also now the free of console port during the close is in the
base VM.

An aux port is allocated to the docker container but not used
for the moment.

Ref https://github.com/GNS3/gns3-gui/issues/1039

gns3server/modules/docker/docker_vm.py

@@ -49,10 +49,12 @@ class DockerVM(BaseVM):
     :param project: Project instance
     :param manager: Manager instance
     :param image: Docker image
+    :param console: TCP console port
+    :param aux: TCP aux console port
     """
 
-    def __init__(self, name, vm_id, project, manager, image, console=None, start_command=None, adapters=None, environment=None):
-        super().__init__(name, vm_id, project, manager, console=console)
+    def __init__(self, name, vm_id, project, manager, image, console=None, aux=None, start_command=None, adapters=None, environment=None):
+        super().__init__(name, vm_id, project, manager, console=console, aux=aux, allocate_aux=True)
 
         self._image = image
         self._start_command = start_command
@@ -62,7 +64,6 @@ class DockerVM(BaseVM):
         self._ubridge_hypervisor = None
         self._temporary_directory = None
         self._telnet_server = None
-        self._closed = False
 
         if adapters is None:
             self.adapters = 1
@@ -84,6 +85,7 @@ class DockerVM(BaseVM):
             "image": self._image,
             "adapters": self.adapters,
             "console": self.console,
+            "aux": self.aux,
             "start_command": self.start_command,
             "environment": self.environment,
             "vm_directory": self.working_dir
@@ -377,11 +379,9 @@ class DockerVM(BaseVM):
     def close(self):
         """Closes this Docker container."""
 
-        if self._closed:
-            return
+        if not (yield from super().close()):
+            return False
 
-        log.debug("Docker container '{name}' [{id}] is closing".format(
-            name=self.name, id=self._cid))
         for adapter in self._ethernet_adapters:
             if adapter is not None:
                 for nio in adapter.ports.values():
@@ -391,10 +391,6 @@ class DockerVM(BaseVM):
 
         yield from self.remove()
 
-        log.info("Docker container '{name}' [{id}] closed".format(
-            name=self.name, id=self._cid))
-        self._closed = True
-
     @asyncio.coroutine
     def _add_ubridge_connection(self, nio, adapter_number, namespace):
         """