should_not_sample_route and should_not_sample_path should not override X-B3-Sampled

[drolando]

With the current logic paths and routes that are blacklisted won't generate a span (and actually interrupt the trace at that point) even if the trace is being sampled. Imo that's not what we usually want.

We usually blacklist paths like /status, /swagger.json or /status/metrics. We do that because we don't want healthchecks and other automated calls to be traced.
But imo if we're in the middle of a trace I'm interested to know if my code is calling the status endpoint of another service and spending time on that.

@adriancole @bplotnick thoughts?