Ingester emitting two identical trace spans for every Push call

[bboreham]

Identical except for slight differences in timing.
Do we add the middleware twice?

[bboreham]

I suspect this, since taking it out makes the symptom go away:

cortex/pkg/cortex/cortex.go

Lines 275 to 276 in f6122f4

	t.Cfg.Server.GRPCMiddleware = append(t.Cfg.Server.GRPCMiddleware,
	tracing.UnaryServerInterceptor(opentracing.GlobalTracer()),

[pracucci]

You're right. I'm checking how we could fix it without loosing Thanos traces (which are quite useful when debugging the blocks storage).