net/http/httputil: reduced log verbosity in reverseproxy_test.go

For functions TestClonesRequestHeaders and TestReverseProxy_PanicBodyError,
I made changes to update the log verbosity.

Fixes #25634

Change-Id: I2a0ef70a8191cfb1a0005949345be722fb4ab62e
Reviewed-on: https://go-review.googlesource.com/115296Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/net/http/httputil/reverseproxy_test.go

@@ -17,6 +17,7 @@ import (
 	"net/http"
 	"net/http/httptest"
 	"net/url"
+	"os"
 	"reflect"
 	"strconv"
 	"strings"
@@ -748,6 +749,8 @@ func TestServeHTTPDeepCopy(t *testing.T) {
 // Issue 18327: verify we always do a deep copy of the Request.Header map
 // before any mutations.
 func TestClonesRequestHeaders(t *testing.T) {
+	log.SetOutput(ioutil.Discard)
+	defer log.SetOutput(os.Stderr)
 	req, _ := http.NewRequest("GET", "http://foo.tld/", nil)
 	req.RemoteAddr = "1.2.3.4:56789"
 	rp := &ReverseProxy{
@@ -824,6 +827,8 @@ func (cc *checkCloser) Read(b []byte) (int, error) {
 
 // Issue 23643: panic on body copy error
 func TestReverseProxy_PanicBodyError(t *testing.T) {
+	log.SetOutput(ioutil.Discard)
+	defer log.SetOutput(os.Stderr)
 	backendServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		out := "this call was relayed by the reverse proxy"
 		// Coerce a wrong content length to induce io.ErrUnexpectedEOF