Do not add HTTP 110 and 111 Warnings to TCP_REFRESH_UNMODIFIED responses.

Do not add HTTP 110 and 111 Warnings to TCP_REFRESH_UNMODIFIED responses.

The old "stale if hit" logic did not account for cases where the stored
stale response became fresh due to a successful revalidation with the
origin server.
When the stored response was stale at the time of the request, we were
adding 110 "Response is stale" and even 111 "Revalidation failed"
Warning headers to responses while logging TCP_REFRESH_UNMODIFIED, which
is considered a hit.