Comment 4 for bug 1668185

Reviewed: https://review.openstack.org/443228
Committed: https://git.openstack.org/cgit/openstack/kolla-ansible/commit/?id=1ae26fac8c2a8839c2f16c618d0ad2423afcf0bc
Submitter: Jenkins
Branch: stable/ocata

commit 1ae26fac8c2a8839c2f16c618d0ad2423afcf0bc
Author: Jeffrey Zhang <email address hidden>
Date: Wed Mar 8 15:04:48 2017 +0800

    Disable running playbooks in serial by default

    Run playbooks in serial are unnecessary and may cause some issue. This
    patch disables serial.

    This patch also removes the serial for MariaDB playbook. MariaDB handle
    this internally.

    Partial-Bug: #1668185
    Change-Id: I3b4216dd82607475e9bd9b44590b631be4abdbdd