Since the auditor will be moving to a different process from the
metainfo loop, we need a way of communicating which segments have
been chosen for audit. This queue will be that communication, for now.
Contrast this with the queue for _re_verifications in commit 9c67f62f.
Refs: https://github.com/storj/storj/issues/5251
Change-Id: I9a269c7ef21e6c5e9c6e5e1f3db298fe159a8a79
