Generate random keystone users

Depends-On: https://gerrit.mcp.mirantis.com/#/c/44319/
Depends-On: https://gerrit.mcp.mirantis.com/#/c/45118/
Depends-On: https://gerrit.mcp.mirantis.com/#/c/45119/

Related-Prod: PROD-29868
Related-Prod: PROD-31315
(cherry picked from commit f5956c2f6151cc5d99659103f90641ea66eac44a)
(cherry picked from commit 70dd0f0587eb297fbefdea43837839c4983b8378)

Change-Id: I402be73437d5397224184a4fd71e2f6abae24db2
diff --git a/galera/server/database/graphite.yml b/galera/server/database/graphite.yml
index 595c16b..fb0582c 100644
--- a/galera/server/database/graphite.yml
+++ b/galera/server/database/graphite.yml
@@ -7,7 +7,7 @@
         graphite:
           encoding: 'utf8'
           users:
-          - name: 'graphite'
+          - name: '${_param:mysql_graphite_username}'
             password: '${_param:mysql_graphite_password}'
             host: '%'
             rights: 'all'