Honor params passed to logout over defaults

[adamjmcgrath]

Description

Additional parameters passed to logout should override the defaults, eg

router.get('/logout', (req, res) =>
      res.oidc.logout({ logoutParams: { id_token_hint: null } })
);

Should allow you to exclude the id_token_hint and force the logout prompt (or supply a logout_hint)

References

fixes #530