Update Galera container config serially
Update Galera container config serially

A change to a galera container's bind mount configuration can cause a
restart of the container. Perform the 'Galera container config' play
serially to avoid a simultaneous restart of all galera containers within
an environment.

Change-Id: I23452067b5d2063e549bbdbb7fe4a08f016313c0
Related-Bug: #1659073

yanyao/openstack-ansible,yanyao/openstack-ansible,openstack/openstack-ansible,robb-romans/openstack-ansible,cfarquhar/openstack-ansible,bunchc/openstack-ansible,BjoernT/os-ansible-deployment,cfarquhar/openstack-ansible,BjoernT/openstack-ansible,stackforge/os-ansible-deployment,os-cloud/os-ansible-deployment,bunchc/openstack-ansible,BjoernT/openstack-ansible,os-cloud/os-ansible-deployment,cloudnull/os-ansible-deployment,openstack/openstack-ansible,cloudnull/os-ansible-deployment,stackforge/os-ansible-deployment,BjoernT/os-ansible-deployment,robb-romans/openstack-ansible,BjoernT/os-ansible-deployment