Today each storagenode should have a port which is opened for the internet, and handles DRPC protocol calls.
When we do a HTTP call on the DRPC endpoint, it hangs until a timeout.
This patch changes the behavior: the main DRPC port of the storagenodes can accept HTTP requests and can be used to monitor the status of the node:
* if returns with HTTP 200 only if the storagnode is healthy (not suspended / disqualified + online score > 0.9)
* it CAN include information about the current status (per satellite). It's opt-in, you should configure it so.
In this way it becomes extremely easy to monitor storagenodes with external uptime services.
Note: this patch exposes some information which was not easily available before (especially the node status, and used satellites). I think it should be acceptable:
* Until having more community satellites, all storagenodes are connected to the main Storj satellites.
* With community satellites, it's good thing to have more transparency (easy way to check who is connected to which satellites)
The implementation is based on this line:
```
http.Serve(NewPrefixedListener([]byte("GET / HT"), publicMux.Route("GET / HT")), p.public.http)
```
This line answers to the TCP requests with `GET / HT...` (GET HTTP request to the route), but puts back the removed prefix.
Change-Id: I3700c7e24524850825ecdf75a4bcc3b4afcb3a74
