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/nova.yml b/galera/server/database/nova.yml
index d2ffc4a..44bfc95 100644
--- a/galera/server/database/nova.yml
+++ b/galera/server/database/nova.yml
@@ -7,12 +7,12 @@
         nova:
           encoding: utf8
           users:
-          - name: nova
+          - name: ${_param:mysql_nova_username}
             password: ${_param:mysql_nova_password}
             host: '%'
             rights: all
             ssl_option: ${_param:mysql_nova_ssl_option}
-          - name: nova
+          - name: ${_param:mysql_nova_username}
             password: ${_param:mysql_nova_password}
             host: ${_param:cluster_local_address}
             rights: all
@@ -20,12 +20,12 @@
         nova_api:
           encoding: utf8
           users:
-          - name: nova
+          - name: ${_param:mysql_nova_username}
             password: ${_param:mysql_nova_password}
             host: '%'
             rights: all
             ssl_option: ${_param:mysql_nova_ssl_option}
-          - name: nova
+          - name: ${_param:mysql_nova_username}
             password: ${_param:mysql_nova_password}
             host: ${_param:cluster_local_address}
             rights: all
@@ -33,12 +33,12 @@
         nova_cell0:
           encoding: utf8
           users:
-          - name: nova
+          - name: ${_param:mysql_nova_username}
             password: ${_param:mysql_nova_password}
             host: '%'
             rights: all
             ssl_option: ${_param:mysql_nova_ssl_option}
-          - name: nova
+          - name: ${_param:mysql_nova_username}
             password: ${_param:mysql_nova_password}
             host: ${_param:cluster_local_address}
             rights: all