Better support for deployment to targets without access to data/stats and RestHeart APIs

[mirzov]

When deployed to a server without data service and RestHeart, the connection pool, used for reading downloads and preview stats for data objects, gets full according to the error log. This appears to result in timeout exceptions for all the data object landing pages. We need to ensure the connection pool does not get full by configuring the HTTP client behavior to quickly fail after one attempt, and allowing more concurrent requests.