Avoid reusing a connection (from pool) when Connection header is set to ...

...close (either in request or response)

If 'Connection: close' header is ignored, connection can be returned to the pool and be reused to send new HTTP requests. However, because the connection is getting closed, it can happen that the request is sent but never received the reply triggering a response timeout. In a load test, it could reach to 10% of timeouts.