Update the ClientSession to use the new timeout parameter.

[robhaswell]

Previously only conn_timeout was being passed to aiohttp.ClientSession, meaning that any long or query would be interrupted after 5 minutes by the default total timeout of 5 minutes.

Additionally the connection timeout does not the original elasticsearch-py API, which specifies that the timeout parameter is the global timeout: https://elasticsearch-py.readthedocs.io/en/master/api.html#timeout

This PR updates the ClientSession instantiation to pass the timeout value to the global timeout.

[cla-checker-service]

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[robhaswell]

OK I have signed the CLA.

[sethmlarson]

Thanks for opening this. This functionality has been captured in elastic/elasticsearch-py#1232