[FIXED JENKINS-23988] Consider CLIAuthenticator for CLIMethods

All `@CLIMethod` based CLI commands failed to authenticate with `--username`/`--password` (or whatever the `SecurityRealm`'s `CLIAuthenticator` expected). `CLICommand`s were successful, so any cursory test of this authentication method using e.g. `help` or  `who-am-i` was successful.

Haven't found a good way to test this, so if anyone has suggestions, they'd be welcome.