Updated image push using preheat - multiple caches retained

[gnr1227]

Bug report:

when we preheat an updated image having same tag name to all the peers, we observed that old and new images cache is available in the cache directory.

Expected behavior:

The old image should automatically retire and replaced with the new one to avoid conflict.

How to reproduce it:

update and preheat the image with same tag name using preheat option -->

Environment:

• Dragonfly version: 2.2.0
• OS: Linux, SUSE 15SP4