[JENKINS-22469] REST/CLI bypasses authentication

This is a fix for [JENKINS-22469] (https://issues.jenkins-ci.org/browse/JENKINS-22469) SpecificUsersAuthorizationStrategy easily bypassed by REST/CLI.

Authentication was not performed when configured via REST/CLI as ``Descriptor#newInstance`` is not called.
Instead, authentication is not performed in ``SpecificUsersAuthorizationStrategy#readResolve``.

As there is no way to retrieve the last configuration in ``readResolve``, "No need for re-authentication" does not work for REST/CLI. That's a limitation.