* Revert "middleware/proxy: Make Unhealthy a pointer (#615)"
This reverts commit acbf522ceb.
* middleware/proxy: add proper locking
This add the proper locking around `Unhealthy`.
Pointer updates are atomic so drop the sync.RWMutex as it is not needed
anymore. This also fixes the race introduced with dfc71df (although I
believe this is the first time we properly tested that code path).
* middleware/proxy: give Exchange a context
Make context.Context the first paramater in the Exchange method.
This is inline with all other query functions.
* up the version
* middleware/proxy: absorb httpproxy
Move the httproxy into proxy. This adds and Exchanger interface which
is used to exchange the messages with the upstream.
The https_google upstream will re-resolve itself and update the upstream
hosts used every 300s.
* Remove and add TODO
