Allowing okhttp event listeners to access the current http span's context

[LikeTheSalad]

Seems like okhttp event listener's callback methods are called before the HTTP span's context becomes the current one for the dispatcher's thread. This causes that calls to Context.curent() within an event listener's method (all of them?) to not return the HTTP span's context.

[serkan-ozal]

Thanks for the issue @LikeTheSalad. As we have discussed in the Slack, while some of the EventListener callbacks (for ex. dnsStart, dnsEnd, secureConnectStart, secureConnectEnd) are called before the actual HTTP request (and so HTTP span), some others are called after it. So at the time of those event callbacks are triggered, there is no active HTTP span's context, so Context.current() returns the outer span (active span just before the OkHTTP client call) or null.