Force timeout to be a float instead of a string

The "timeout" kwarg expects a Float to be passed through, but the _escape function returns the "request_timeout" argument as a string here:  https://github.com/elasticsearch/elasticsearch-py/blob/c112399631a9bfb8517f1483051c5ba5510951e6/elasticsearch/client/utils.py#L62

"request_timeout" gets popped and passed into def perform_request() as the "timeout" argument as a string, leading to a type error.

casting to a float() seems to fix it.