Conflicts introduced by recreating docs with attachments

When a document is re-created with an attachment it receives a non-deterministic revision. This is due to a fairly old commit [1] that introduced the behavior by accidentally including information about revisions on disk into the revision id calculation when the revision id was being calculated by couch_db_updater when it realized that the update was re-creating a document that was previously deleted.

I'm opening a PR with the fix.

[1] https://github.com/apache/couchdb-couch/commit/08a94d582cd3086ebcbd51ad8ac98ca6df98a1b7