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/keystone/client/os_client_config/octavia_identity.yml b/keystone/client/os_client_config/octavia_identity.yml
index 3d84b0c..8dabc3f 100644
--- a/keystone/client/os_client_config/octavia_identity.yml
+++ b/keystone/client/os_client_config/octavia_identity.yml
@@ -12,7 +12,7 @@
                   identity_api_version: '3'
                   interface: 'internal'
                   auth:
-                    username: 'octavia'
+                    username: '${_param:keystone_octavia_username}'
                     password: ${_param:keystone_octavia_password}
                     user_domain_name: 'Default'
                     project_name: 'service'