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/sahara/server/cluster.yml b/sahara/server/cluster.yml
index b01ab3d..3e48e7d 100644
--- a/sahara/server/cluster.yml
+++ b/sahara/server/cluster.yml
@@ -18,7 +18,7 @@
         host: ${_param:openstack_database_address}
         port: 3306
         name: sahara
-        user: sahara
+        user: ${_param:mysql_sahara_username}
         password: ${_param:mysql_sahara_password}
       identity:
         engine: keystone
@@ -26,7 +26,7 @@
         host:  ${_param:openstack_control_address}
         port: 35357
         tenant: service
-        user: sahara
+        user: ${_param:keystone_sahara_username}
         password: ${_param:keystone_sahara_password}
       message_queue:
         engine: rabbitmq