Object names of directory objects qualified for ExpiredObjectAllVersions
must be encoded appropriately before calling on deletePrefix on their
erasure set.
e.g., a directory object and regular objects with overlapping prefixes
could lead to the expiration of regular objects, which is not the
intention of ILM.
```
bucket/dir/ ---> directory object
bucket/dir/obj-1
```
When `bucket/dir/` qualifies for expiration, the current implementation would
remove regular objects under the prefix `bucket/dir/`, in this case,
`bucket/dir/obj-1`.
