In order to make easy orchestration on all OpenStack db-sync, add this
tag so people can use this tag in composition layer.
A use case it to set some orchestration to make sure MySQL Galera is
ready before running any Exec with this tag.
Change-Id: Idfcbaa2d137c91a464fb5d49ae25fa348c67d642
Closes-Bug: #1755102
(cherry picked from commit fd3b9d6681)