Can't pass in options to opentracing handler

[gouthamve]

So, the query endpoint AND the /metrics endpoint both end up under the operation: "HTTP GET" and this clutters up a traces a fair bit.

We could pass in something like this: https://godoc.org/github.com/opentracing-contrib/go-stdlib/nethttp#OperationNameFunc to differentiate both but because opentracing is a default middleware, there is no way to do that, see: https://github.com/weaveworks/common/blob/master/middleware/http_tracing.go#L17

Now, we can pass in the options to the tracer, but would you open to adding something like OpentracingOptions to server.Config?

[bboreham]

The specific problem described was addressed at #126. Do you still need options?