fix flaky ext auth e2e (envoyproxy#3221)

Signed-off-by: huabing zhao <zhaohuabing@gmail.com>

test/e2e/tests/ext_auth_http_service.go

@@ -78,15 +78,7 @@ var HTTPExtAuthTest = suite.ConformanceTest{
 				Namespace: ns,
 			}
 
-			req := http.MakeRequest(t, &expectedResponse, gwAddr, "HTTP", "http")
-			cReq, cResp, err := suite.RoundTripper.CaptureRoundTrip(req)
-			if err != nil {
-				t.Errorf("failed to get expected response: %v", err)
-			}
-
-			if err := http.CompareRequest(t, &req, cReq, cResp, expectedResponse); err != nil {
-				t.Errorf("failed to compare request and response: %v", err)
-			}
+			http.MakeRequestAndExpectEventuallyConsistentResponse(t, suite.RoundTripper, suite.TimeoutConfig, gwAddr, expectedResponse)
 		})
 
 		t.Run("without Authorization header", func(t *testing.T) {