Add default params for backup

Change-Id: I9640ad13cb8838ab7afb014280cb12d15487a02e
Related: PROD-27557 (PROD:27557)
diff --git a/defaults/init.yml b/defaults/init.yml
index 42c315a..978671c 100644
--- a/defaults/init.yml
+++ b/defaults/init.yml
@@ -22,6 +22,7 @@
 - system.defaults.salt
 - system.defaults.stacklight
 - system.defaults.xtrabackup
+- system.defaults.backup
 parameters:
   _param:
     mcp_version: stable