user context not passed down in fabric_view_all_docs

We omitted to pass user_ctx down in fabric_view_all_docs. Since auth has happened beforehand this hasn't been an obvious issue, but it matters for the _users db as that reacts differently based on the user. couchdb intentionally hides design documents in that database from non-admins and intentionally hides the user docs of other users.

passing the user ctx down fixes both issues.