Fixed a bug where if a ClaimsPrincipal was set by a piece of middleware in the seucrity pipleine, the default authentication middleware would inadvertently log a blank warning message since it didn't perform the authentication itself. The middleware now only logs messages if it attempts the authentication itself

Fixed a bug where if a authorization challenge result was set by a piece of middleware in the security pipeline, the default authorization middleware would inadvertently log the challenge result , even when it did not determine this result itself. This could result double logging in some use scenarios. The default authorization component will now only log a challenge result it if produces the result itself.