* s3api: test that a session token must not reveal its credential
* sts: derive secret access key with HMAC keyed on the signing key
* s3api: stop accepting STS session tokens as bearer credentials
* security: reject STS session tokens on filer and admin gRPC auth
* test: sign s3/iam framework requests with the session credential
* s3api: exercise the real auth pipeline in the end-to-end harness