Remove @staticmethod from functions outside classes

[anthonychu]

Got some of these errors accessing functions in http_util.py due to @staticmethod decorator on functions outside classes:

Microsoft.Azure.WebJobs.Host.FunctionInvocationException: Exception while executing function: Functions.HttpTrigger
 ---> Microsoft.Azure.WebJobs.Script.Workers.Rpc.RpcException: Result: Failure
Exception: TypeError: 'staticmethod' object is not callable
Stack:   File "/azure-functions-host/workers/python/3.7/LINUX/X64/azure_functions_worker/dispatcher.py", line 312, in _handle__invocation_request
    call_result = await fi.func(**args)
  File "/home/site/wwwroot/HttpTrigger/__init__.py", line 9, in main
    instance_id = await client.start_new("HelloOrchestrator", None, "Seattle")
  File "/usr/local/lib/python3.7/site-packages/azure/durable_functions/models/DurableOrchestrationClient.py", line 71, in start_new
    response = await self._post_async_request(request_url, self._get_json_input(client_input))
  File "/usr/local/lib/python3.7/site-packages/azure/durable_functions/models/DurableOrchestrationClient.py", line 40, in <lambda>
    self._post_async_request = lambda u, d: post_async_request(u, d)