GDM hangs when system is configured with sssd for AD authentication, unable to login graphically (GUI)

Issue

• GDM hangs after configuring system with sssd for AD auhentication, AD login fails
• GDM fails to start in runlevel 5 and unable to login as AD user via sssd. /var/log/secure shows:

Nov  5 17:30:37 server-01 gdm-launch-environment]: pam_sss(gdm-launch-environment:account): Access denied for user gdm: 10 (User not known to the underlying authentication module)
...
Nov  5 17:31:09 server-01 gdm-password]: pam_unix(gdm-password:auth): check pass; user unknown
Nov  5 17:31:09 server-01 gdm-password]: pam_unix(gdm-password:auth): authentication failure; logname= uid=0 euid=0 tty= ruser= rhost=
Nov  5 17:31:09 server-01 gdm-password]: pam_sss(gdm-password:auth): authentication failure; logname= uid=0 euid=0 tty= ruser= rhost= user=ad_user01
Nov  5 17:31:09 server-01 gdm-password]: pam_sss(gdm-password:auth): received for user ad_user01: 10 (User not known to the underlying authentication module)
Nov  5 17:31:09 server-01 gdm-password]: gkr-pam: error looking up user information
...
Nov  5 17:32:55 server-01 gdm-launch-environment]: pam_sss(gdm-launch-environment:account): Access denied for user gdm: 10 (User not known to the underlying authentication module)
...
Nov  5 17:36:23 server-01 gdm-launch-environment]: pam_sss(gdm-launch-environment:account): Request to sssd failed. Connection refused

• Everything runs perfect in runlevel 3. On commenting 'pam_sss.so' from 'account' section of PAM, GDM seems to load but login fails. Everything works perfect if you start system in runlevel 3 and so 'startx'