Resolve "fix(ynh_backup): fix purging system for YNH backups"

Closes #82 (closed)

roles/ynh_backup/templates/ynh_backup.sh.j2

@@ -22,6 +22,7 @@ _prune_old_backup() {
     for backup in $old_backup_list; do
       echo "Backup $backup is 2 days old or more. Purging it now."
       yunohost backup delete "$backup"
+      rm -rf backup_"$backup"
     done
     _good "Purging of old backups completed."
   else