all: Propagate opentracing headers
Created by: keegancsmith
In an old refactor were we switched to using ctxhttp more, we regressed on propogating the opentracing headers across RPC calls. This was due to nethttp.TraceRequest modifying the request's context. However, we would then do ctxhttp which would update the context before the call to nethttp.TraceRequest. This lead to nethttp.Transport not finding the request span to inject.
Also changed in this commit:
- Upgrade opentracing libraries
- Remove unneeded span from gitserver.exec
Fixes https://github.com/sourcegraph/sourcegraph/issues/3253