firewalld service is failing and unable to start in RHEL 7

Issue

• firewalld is failing to start as shown below;

  # systemctl restart firewalld.service
  Job for firewalld.service failed. See 'systemctl status firewalld.service' and 'journalctl -xn' for details.
  

• Below are the logs which provided more details of the failed firewalld service:

  # systemctl status firewalld.service -l
  firewalld.service - firewalld - dynamic firewall daemon
     Loaded: loaded (/usr/lib/systemd/system/firewalld.service; enabled)
     Active: failed (Result: timeout) since Mon 2014-07-07 13:49:26 BST; 7min ago
   Main PID: 20708
  
  Jul 07 13:47:55 HOSTNAME systemd[1]: Starting firewalld - dynamic firewall daemon...
  Jul 07 13:49:25 HOSTNAME systemd[1]: firewalld.service operation timed out. Terminating.
  Jul 07 13:49:26 HOSTNAME systemd[1]: Failed to start firewalld - dynamic firewall daemon.
  Jul 07 13:49:26 HOSTNAME systemd[1]: Unit firewalld.service entered failed state.
  
  # journalctl -xn
  -- Logs begin at Fri 2014-06-13 19:52:40 BST, end at Mon 2014-07-07 13:50:01 BST
  Jul 07 13:47:55 HOSTNAME kernel: nf_conntrack version 0.5.0 (16384 buckets, 6
  Jul 07 13:47:55 HOSTNAME kernel: ip6_tables: (C) 2000-2006 Netfilter Core Tea
  Jul 07 13:47:55 HOSTNAME kernel: Ebtables v2.0 registered
  Jul 07 13:49:25 HOSTNAME systemd[1]: firewalld.service operation timed out. T
  Jul 07 13:49:26 HOSTNAME kernel: Ebtables v2.0 unregistered
  Jul 07 13:49:26 HOSTNAME systemd[1]: Failed to start firewalld - dynamic fire
  -- Subject: Unit firewalld.service has failed
  -- Defined-By: systemd
  -- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
  --
  -- Unit firewalld.service has failed.
  --
  -- The result is failed.
  Jul 07 13:49:26 HOSTNAME systemd[1]: Unit firewalld.service entered failed st
  Jul 07 13:50:01 HOSTNAME systemd[1]: Starting Session 4064 of user root.
  -- Subject: Unit session-4064.scope has begun with start-up
  -- Defined-By: systemd
  -- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
  --
  -- Unit session-4064.scope has begun starting up.
  Jul 07 13:50:01 HOSTNAME systemd[1]: Started Session 4064 of user root.
  -- Subject: Unit session-4064.scope has finished start-up
  lines 1-23
  

• What is causing all of these firewalld errors?
• Docker was used/configured on the system before , after stopping docker when firewalld service was tried to start , it gave above error.