issue #434: tests: set a default remote_user in ansible.cfg.

tests/ansible/ansible.cfg

@@ -13,6 +13,9 @@ retry_files_enabled = False
 display_args_to_stdout = True
 forks = 100
 
+# issue #434; hosts/delegate_to; integration/delegate_to
+remote_user = ansible-cfg-remote-user
+
 # On MacOS, "smart" with a password set causes Ansible to use paramiko.
 transport = ssh