Use default retry logic in requests adapter (which is zero).

[jsiembida]

The original commit doesn't explain why retry=3 was introduced in the first place.
Before, it was default, zero. Now it seems to conflict with retry decorator used
in some call in managers code resulting in 16 retries in total when combined.

[coveralls]

Coverage decreased (-0.002%) to 91.773% when pulling aa67c28 on jsiembida:reduntant-retry-logic-removal into cfab07e on softlayer:master.

[allmightyspiff]

The retry decorator exists to retry application errors, and the retry adapter exists to retry connection errors.

Having them retry the same error is certainly not intended for sure, but removing the retry adapter isn't the solution.

I think removing the exceptions.TransportError from the RETRIABLE in https://github.com/softlayer/softlayer-python/blob/master/SoftLayer/decoration.py will fix the 16 retries issue. If you want to test that out and change your pull request I'll merge it.

I'm also ok with tuneing down the retries to 2 each, but the retry adapter needs to be kept in.

[allmightyspiff]

To fix the Retry adapter and the Retry decorator both activating, remove the TransportError exception from the retry decorator instead.

[allmightyspiff]

I've fixed this in #1150 by removing TransportError from one of the retryable errors.