@Test void healthcheck_usesB3Single() {
    server.enqueue(VERSION_RESPONSE.toHttpResponse());
    server.enqueue(YELLOW_RESPONSE.toHttpResponse());

    assertThat(storage.check().ok()).isTrue();

    assertThat(server.takeRequest().request().headers())
      .extracting(e -> e.getKey().toString())
      .contains("b3")
      .doesNotContain("x-b3-traceid");
  }
We currently don't have a nice way to mute outbound propagation in Brave. This just makes sure
we are nicer.
zipkin-server/src/test/java/zipkin2/server/internal/elasticsearch/ITElasticsearchSelfTracing.java