* provider/openstack: Expose LogRoundTripper fields externally
* state/remote/swift: Add support for debugging Openstack calls using
OS_DEBUG env variable.
* provider/openstack: Update LogRoundTripper to log headers aswell as body.
* Add `RedactHeaders` function in order to redact sensitive http Headers.
Refactor `logRequest` and `logResponse` to use `RedactHeaders` func.