Merge pull request #1617 from howardjohn/conformance/drop-default-client

conformance: do not use (and mutate) DefaultClient

conformance/utils/roundtripper/roundtripper.go

@@ -95,7 +95,7 @@ type DefaultRoundTripper struct {
 // is received.
 func (d *DefaultRoundTripper) CaptureRoundTrip(request Request) (*CapturedRequest, *CapturedResponse, error) {
 	cReq := &CapturedRequest{}
-	client := http.DefaultClient
+	client := &http.Client{}
 
 	if request.UnfollowRedirect {
 		client.CheckRedirect = func(req *http.Request, via []*http.Request) error {