Andrey Smirnov e658c442a6 feat: implement grpc request loggging
Logging is pretty simple and bare minimum is being logged. I believe
better logging can be provided for apid when it does fan-out, but that
is beyond the scope for the first PR.

Sample logs:

```
$ osctl-linux-amd64 logs machined-api
machined 2019/11/11 21:16:43 OK [/machine.Machine/ServiceList] 0.000ms unary Success (:authority=unix:/run/system/machined/machine.sock;content-type=application/grpc;user-agent=grpc-go/1.23.0)
machined 2019/11/11 21:17:09 Unknown [/machine.Machine/Logs] 0.000ms stream open /run/system/log/machined.log: no such file or directory (:authority=unix:/run/system/machined/machine.sock;content-type=application/grpc;user-agent=grpc-go/1.23.0)
```

Signed-off-by: Andrey Smirnov <smirnov.andrey@gmail.com>
2019-11-11 13:42:08 -08:00
..
2019-11-11 13:42:08 -08:00