Description of problem: Overcloud deployment fails with connection to mysql error. Mariadb service crashed on instack instance after failed install. Overcloud state is stuck at "creating". 


Guide followed: https://repos.fedorapeople.org/repos/openstack-m/rdo-manager-docs/liberty/index.html


Version-Release number of selected component (if applicable):
lsb_release -a
LSB Version:    :core-4.1-amd64:core-4.1-noarch
Distributor ID: CentOS
Description:    CentOS Linux release 7.2.1511 (Core)
Release:        7.2.1511
Codename:       Core

Using CentOS RDO release or Delorean. Same issue faced with both. 

How reproducible: Attempt virtual environment install using default NODE_MEM value on baremetal always fail with this error. 


Steps to Reproduce:
1. Perform standard RDO install using default NODE_MEM value of 4096. Follow guide until you reach the step in point 2. 

2. openstack overcloud deploy. I have reproduced this with or without ceph (with 2 or 3 baremetal VMs, depending)

Actual results:
mariadb crashes when the instack instance runs out of memory, causing the install to fail and the deploy to get stuck until it times out. (unable to delete it)

Expected results:
Default values should provide a system capable of performing the install. 

Additional info:
I have set 2gig of swapfile on the instack instance prior to re-launching the deployment. Install completed with top showing a max swap usage of 550668 during the install.