Apache bRPC: improper authentication

Improper authentication in Apache bRPC through 1.17.0 allows a remote unauthenticated attacker to bypass authentication for protected non-builtin HTTP endpoints by first sending a builtin HTTP request on the same HTTP/1.1 keep-alive connection.

When ServerOptions.auth is enabled and builtin HTTP services are exposed on the public listener, a builtin request received as the first message on a socket may cause the connection to be treated as authenticated for later requests on that socket. Users are recommended to upgrade to version 1.18.0, which fixes this issue, or apply this PR separately: https://github.com/apache/brpc/pull/3308