Deactivate workers for windows

Authenticationworker and rsyslog workers are not supported on windows yet. The authentication worker will be ported on windows to add support for winrm. Rsyslog is not supported on windows yet.

This pull request depends on https://github.com/juju/juju/pull/244
It doesn't actually matter, but I generally prefer to use m := map[string]string{}  rather than using make.  It's one less thing to read... the make is really extraneous.