To avoid large delays in metacache cleanup, use rename
instead of recursive delete calls, renames are cheaper
move the content to minioMetaTmpBucket and then cleanup
this folder once in 24hrs instead.
If the new cache can replace an existing one, we should
let it replace since that is currently being saved anyways,
this avoids pile up of 1000's of metacache entires for
same listing calls that are not necessary to be stored
on disk.
Additional cases handled
- fix address situations where healing is not
triggered on failed writes and deletes.
- consider object exists during listing when
metadata can be successfully decoded.