Major Description
The feature implemented in MRESOLVER-315 is broken when default HTTP or HTTPS ports (80 or 443 respectively) are used, as in majority of public servers.
The SharingAuthCache "converts" the HttpHost to port-normalized one, but the code to activate preemptive tampers directly with shared state (not AuthCache), hence in these cases, it is not activated properly due key mismatch. Ironically, as UT does test this feature but are unable to open ports 80 or 443, the feature works ok.
Fix: migrate to HttpClient 4.3+ HttpClientContext that has type safe setters/getters exposed, and HttpTransport should do things "by the book" (use authCache) that underlying implementation them sorts out proper keying.