Generate random keystone users

Change-Id: I8dbd07b10d29b43d1c35fa76bcaa0f0efb32beda
Related-Prod: PROD-29868
diff --git a/galera/server/database/tacker.yml b/galera/server/database/tacker.yml
index 9cd76b5..d181450 100644
--- a/galera/server/database/tacker.yml
+++ b/galera/server/database/tacker.yml
@@ -7,12 +7,12 @@
         tacker:
           encoding: utf8
           users:
-          - name: tacker
+          - name: ${_param:mysql_tacker_username}
             password: ${_param:mysql_tacker_password}
             host: '%'
             rights: all
             ssl_option: ${_param:mysql_tacker_ssl_option}
-          - name: tacker
+          - name: ${_param:mysql_tacker_username}
             password: ${_param:mysql_tacker_password}
             host: ${_param:cluster_local_address}
             rights: all