On some systems, we have seen gdm unable to start because it doesn't find
the gnome-initial-setup user.  We will never have gnome-initial-setup user
and shouldn't have gnome-intial-setup start with gdm as the username, so 
disabling it in the conf file.

--- gdm-3.18.2/data/gdm.conf-custom.in	2017-02-16 13:55:47.788461253 -0800
+++ gdm-3.18.2/data/gdm.conf-custom.in	2017-02-16 13:56:07.933402043 -0800
@@ -1,6 +1,7 @@
 # GDM configuration storage
 
 [daemon]
+InitialSetupEnable=False
 
 [security]