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: I869ed64d19d82c64d6370a6b42c3016087f5760d
Closes-Bug: #1755102
(cherry picked from commit 635bbc2a47)