parametrize backup server side dir

PROD-18191

Change-Id: I15c2cc66f0c0010408863b46c0dccf84730f31d9
diff --git a/README.rst b/README.rst
index cd9abc6..116548b 100644
--- a/README.rst
+++ b/README.rst
@@ -225,6 +225,7 @@
         backup: true
         initial_data:
           engine: backupninja
+          home_dir: remote-backup-home-dir
           source: backup-node-host
           host: original-salt-master-id