Catch a timeout error in docker

Fix #936

gns3server/compute/docker/docker_vm.py

@@ -768,7 +768,7 @@ class DockerVM(BaseNode):
         Pull image from docker repository
         """
         log.info("Pull %s from docker hub", image)
-        response = yield from self.manager.http_query("POST", "images/create", params={"fromImage": image})
+        response = yield from self.manager.http_query("POST", "images/create", params={"fromImage": image}, timeout=None)
         # The pull api will stream status via an HTTP JSON stream
         content = ""
         while True:

tests/compute/docker/test_docker_vm.py

@@ -819,7 +819,7 @@ def test_pull_image(loop, vm):
 
     with asyncio_patch("gns3server.compute.docker.Docker.http_query", return_value=mock_query) as mock:
         images = loop.run_until_complete(asyncio.async(vm.pull_image("ubuntu")))
-        mock.assert_called_with("POST", "images/create", params={"fromImage": "ubuntu"})
+        mock.assert_called_with("POST", "images/create", params={"fromImage": "ubuntu"}, timeout=None)
 
 
 def test_start_capture(vm, tmpdir, manager, free_console_port, loop):