MB-7569 Ignore eacces errors on delete dir init

Ignore those and have index cleanup delete any files in
that directory too. Index cleanup is already periodically
called by the compaction scheduler (ns_server), so that we
don't risk having files in the delete directory that are
never deleted.

Change-Id: Ib55bdeab07deed876822c21acacbfebda7fb639e
Reviewed-on: http://review.couchbase.org/24398
Reviewed-by: Sriram Melkote <siri.couchbase@gmail.com>
Reviewed-by: Filipe David Borba Manana <fdmanana@gmail.com>
Tested-by: Filipe David Borba Manana <fdmanana@gmail.com>