Add default params for backup

Change-Id: I9640ad13cb8838ab7afb014280cb12d15487a02e
Related: PROD-27557 (PROD:27557)
(cherry-picked from commit aec00ff6feb91b751b505b6613a85cfec05447e4)
diff --git a/defaults/init.yml b/defaults/init.yml
index c90c404..12ced59 100644
--- a/defaults/init.yml
+++ b/defaults/init.yml
@@ -26,6 +26,7 @@
 - system.defaults.secrets
 - system.defaults.stacklight
 - system.defaults.xtrabackup
+- system.defaults.backup
 - system.defaults.haproxy
 parameters:
   _param: