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: I7baded10a128532f7267903fa8d14f576cd9f47a
Closes-Bug: #1755102
(cherry picked from commit 90863dce61)