Increase health check timeout to 10min

Unfortunate, but we need this sometime to wait
for a new node to come up.

hub.py

@@ -312,7 +312,7 @@ async def check_hub_health(self, test_notebook_path, service_api_token):
                 hub_url,
                 test_notebook_path,
                 username=username,
-                server_creation_timeout=300,
+                server_creation_timeout=600,
                 kernel_execution_timeout=300, # This doesn't do anything yet
                 create_user=True,
                 delete_user=False, # To be able to delete its server in case of failure