LIBDRUM-1005. "Restricted Access" pages return 401/403 to bots

Corrects Google Search reports of "Soft 404" errors for the
"Restricted Access" pages returned when a DSpace bitstream is embargoed
or otherwise not available but returning either "401 Unauthorized" for
anonymous users, or "403 Forbidden" for unauthorized users.

This change only affects the Angular server-side rendering (SSR)
functionality that is triggered by bots -- regular users will still
see a "Restricted Access" page with a 200 OK response.

https://umd-dit.atlassian.net/browse/LIBDRUM-1005

Author: dsteelma-umd