fixed bug in etcd retention where backups are not sorted by date (#6860)

* fixed bug in etcd retention where backups are not sorted by date

* added directory filter to find command

roles/etcd/handlers/backup.yml

@@ -62,5 +62,5 @@
 - name: Remove old etcd backups
   shell:
     chdir: "{{ etcd_backup_prefix }}"
-    cmd: "find . -name 'etcd-*' | head -n -{{ etcd_backup_retention_count }} | xargs rm -rf"
+    cmd: "find . -name 'etcd-*' -type d | sort -n | head -n -{{ etcd_backup_retention_count }} | xargs rm -rf"
   when: etcd_backup_retention_count >= 0