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/designate/server/single.yml b/designate/server/single.yml
index f054b0c..8f07ffb 100644
--- a/designate/server/single.yml
+++ b/designate/server/single.yml
@@ -34,7 +34,7 @@
         name:
           main_database: designate
           pool_manager: designate_pool_manager
-        user: designate
+        user: ${_param:mysql_designate_username}
         password: ${_param:mysql_designate_password}
         x509:
           enabled: ${_param:openstack_mysql_x509_enabled}
@@ -48,7 +48,7 @@
         host: ${_param:single_address}
         port: 35357
         tenant: service
-        user: designate
+        user: ${_param:keystone_designate_username}
         password: ${_param:keystone_designate_password}
         protocol: ${_param:internal_protocol}
       message_queue: