Fix login_as / logout_from workflow forms
When using real text-/passwordinputs browser try filling them with stored user/password pairs. With some variants of browser (seen in firefox and chrome) it make trouble:
- them ignore a
- Some browser versions do not use the "value" attribute on post, especially for Chrome, them use the (wrong) auto filled in values instead.
This means that a "login as" fails if a username / password combination is stored. So using these fields as hidden input is the better solution.