Clustercheck, monitor service for galera containers

Clustercheck, monitor service for galera containers

In HA overcloud deployments, HAProxy makes use of a helper service
called "clustercheck", to check whether galera nodes are available for
serving traffic.

This change implements a dedicated profile for clustercheck, which was
originally part of the pacemaker mysql profile. The profile generates
the necessary configuration files for clustercheck and let heat
templates manage the associated container's lifecycle.

Co-Authored-By: Michele Baldessari <michele@acksyn.org>
Partial-Bug: #1692969
Change-Id: I1aabe34fa6a9c8c705a4405f275b66502c313cf2