Clean up nock usage

[mdrichardson]

This is a tracking issue that I'll address after we decide how we want to an SDK-wide issue that impacts this

Issues

• nock-helper breaks nock for other tests because it overrides pieces of Node's http module. Caused this issue
• I believe we call nock.restore() and nock.cleanAll() in ways that will make running tests in parallel very difficult or impossible

To Fix

1. Remove nock-helper and replace calls to it with the appropriate nock method.
2. Ensure we don't call nock.cleanAll() and nock.restore() more than absolutely necessary