Generate random keystone users

Change-Id: I8dbd07b10d29b43d1c35fa76bcaa0f0efb32beda
Related-Prod: PROD-29868
diff --git a/mysql/client/database_upgrade/sahara.yml b/mysql/client/database_upgrade/sahara.yml
index 73618d0..414b3dc 100644
--- a/mysql/client/database_upgrade/sahara.yml
+++ b/mysql/client/database_upgrade/sahara.yml
@@ -7,11 +7,11 @@
             sahara_upgrade:
               encoding: utf8
               users:
-              - name: sahara
+              - name: ${_param:mysql_sahara_username}
                 password: ${_param:mysql_sahara_password}
                 host: '%'
                 rights: all
-              - name: sahara
+              - name: ${_param:mysql_sahara_username}
                 password: ${_param:mysql_sahara_password}
                 host: ${_param:single_address}
                 rights: all