NEXUS-6139: Evict unused items deletes permanently.

Seemingly we have duplicated walker processors used by
Maven proxies and everything else. The latter was
already fixed by this PR below:
https://github.com/sonatype/nexus-oss/pull/262

But as Rich detected, the fix was not applied to
Maven repositories.
NEXUS-6139: Fix IT

As originally it expected that files will land in
trash and hence, no empty directory will exist in there.
Merge pull request #286 from sonatype/NEXUS-6139-evict-no-trash

NEXUS-6139: Evict unused items deletes permanently.