Make containerized galera use mysql_network everywhere

Make containerized galera use mysql_network everywhere

The containerized galera service generates a galera.cnf which uses
short hostname to identify itself rather than the fqdn from the
mysql_network (e.g. overcloud-x.internalapi.cloudname).

This breaks when internal TLS is in use, because the mysql certificate
does not reference this short hostname.

Fix the appropriate hiera parameter to make it behave like the
non-containerized galera service.

Change-Id: I904cde38f2baeddab5178e8ad48d34a0c73629af
Closes-Bug: #1719599
(cherry picked from commit e10aa591dc9155a2746df01279c4ba4f2133fd17)