* `Get()` now returns immediately when context is done during a groupcache peer
conversation. Previously `Get()` would call the `Getter` with a done context.
This change caused a data race during async calls to groupcache.Get().
Also discovered `DefaultTransport` has per address connection pooling
only when the request was a success, which is sufficient for most use
cases.
* Now Associating the transport with peer `httpGetter` so we take advantage of
connection reuse. This lowers the impact on DNS and improves preformance for
high request volume low latency applications.
* Now always populating the hotcache. A more complex algorithm is unnecessary
when the LRU cache will ensure the most used values remain in the cache. The
evict code ensures the hotcache does not over crowd the maincache.
