Added `retry` argument to `request()` method in Python library.
Added `retry` argument to `request()` method in Python library.

This allows us to do HTTP requests without using `tenacity.retry()`. We
need to be able to disable these retries to stream data for a long
period of time, such as when using the upcoming `mesos task exec`.

Review: https://reviews.apache.org/r/69023

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