MB-9847 Remove "web request failed" errors from user-visible log.

Change-Id: I72cdbf50a3f99ea316d07cddebde4d40ff4431b0
Reviewed-on: http://review.couchbase.org/33017
Reviewed-by: Artem Stemkovski <artem@couchbase.com>
Tested-by: Artem Stemkovski <artem@couchbase.com>