net/http: rename tests for Redirect and StripPrefix

Before May 2018, I mistakenly thought the _suffix naming convention¹
used by examples also applied to tests. Thanks to a code review comment²
from Ian Lance Taylor, I have since learned that is not true.
This trivial change fixes some collateral damage from my earlier
misunderstanding, resulting in improved test naming consistency.

¹ https://golang.org/pkg/testing/#hdr-Examples
² https://go-review.googlesource.com/c/go/+/112935/1/src/path/filepath/path_test.go#1075

Change-Id: I555f60719629eb64bf2f096aa3dd5e00851827cd
Reviewed-on: https://go-review.googlesource.com/c/go/+/207446
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/net/http/serve_test.go

@@ -2632,7 +2632,7 @@ func TestRedirect(t *testing.T) {
 
 // Test that Redirect sets Content-Type header for GET and HEAD requests
 // and writes a short HTML body, unless the request already has a Content-Type header.
-func TestRedirect_contentTypeAndBody(t *testing.T) {
+func TestRedirectContentTypeAndBody(t *testing.T) {
 	type ctHeader struct {
 		Values []string
 	}
@@ -2911,7 +2911,7 @@ func TestStripPrefix(t *testing.T) {
 }
 
 // https://golang.org/issue/18952.
-func TestStripPrefix_notModifyRequest(t *testing.T) {
+func TestStripPrefixNotModifyRequest(t *testing.T) {
 	h := StripPrefix("/foo", NotFoundHandler())
 	req := httptest.NewRequest("GET", "/foo/bar", nil)
 	h.ServeHTTP(httptest.NewRecorder(), req)