The X-Auth-Token is sensitive data. If revealed to an unauthozied person,
they can now make requests against an account until the token expires.
This implementation maintains current behavior (i.e, the token
is logged). Implementers can choose to set reveal_sensitive_prefix
to (e.g.) 12 so only first 12 characters of the token are logged.
Or, set to 0 to replace the token with "...".
DocImpact
Part of bug #1004114
Change-Id: Iecefa843d8f9ef59b9dcf0860e7a4d0e186a6cb5