MB-11722: Remove the mcCouch dependency

Now,
- unlinking stale files at the end of compaction
- unlinking files in couchkvstore reset
- unlink files in delVbucket

Change-Id: I000fbd076856b8de1a0dcb82aa673b3316dc745f
Reviewed-on: http://review.couchbase.org/40195
Reviewed-by: Michael Wiederhold <mike@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>