services: gdm: Remove 'allow-root?' option.

This option results in allowing all login attempts without asking for
credentials.  The name is confusing, but rather than rename it, we will
remove it, since it seems like a feature that no one would want.

* gnu/services/xorg.scm (<gdm-configuration>): Remove 'allow-root?'.
(gdm-pam-service): Do not use 'gdm-configuration-allow-root?'.

Signed-off-by: Danny Milosavljevic <dannym@scratchpost.org>

gnu/services/xorg.scm

@@ -2,6 +2,7 @@
 ;;; Copyright © 2017 Andy Wingo <wingo@igalia.com>
 ;;; Copyright © 2013, 2014, 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2015 Sou Bunnbu <iyzsong@gmail.com>
+;;; Copyright © 2018 Timothy Sample <samplet@ngyro.com>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -625,7 +626,6 @@ makes the good ol' XlockMore usable."
   gdm-configuration?
   (gdm gdm-configuration-gdm (default gdm))
   (allow-empty-passwords? gdm-configuration-allow-empty-passwords? (default #t))
-  (allow-root? gdm-configuration-allow-root? (default #t))
   (auto-login? gdm-configuration-auto-login? (default #f))
   (default-user gdm-configuration-default-user (default #f))
   (x-server gdm-configuration-x-server))
@@ -680,10 +680,9 @@ makes the good ol' XlockMore usable."
     (auth (list (pam-entry
                  (control "required")
                  (module "pam_permit.so")))))
-   (unix-pam-service
-    "gdm-password"
-    #:allow-empty-passwords? (gdm-configuration-allow-empty-passwords? config)
-    #:allow-root? (gdm-configuration-allow-root? config))))
+   (unix-pam-service "gdm-password"
+                     #:allow-empty-passwords?
+                     (gdm-configuration-allow-empty-passwords? config))))
 
 (define (gdm-shepherd-service config)
   (list (shepherd-service