[fix] fixed https://github.com/osiam/addon-self-administration/issues/63

- when the password reset was already done by the user a FORBIDDEN with an error
  description will be returned
can you reword this sentence without using a gender-specific pronoun? we cannot know the gender of the user at this point. alternatively, you can change `his` to a singular `their` (see http://en.wikipedia.org/wiki/Singular_they)