net/http: deflake TestLinuxSendfile

Fixes #17805

Change-Id: I30d3e63a82b3690a76f2bb33d59ae34c62a7fa59
Reviewed-on: https://go-review.googlesource.com/32759
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/net/http/fs_test.go

@@ -1116,10 +1116,9 @@ func TestLinuxSendfile(t *testing.T) {
 	Post(fmt.Sprintf("http://%s/quit", ln.Addr()), "", nil)
 	child.Wait()
 
-	rx := regexp.MustCompile(`sendfile(64)?\(\d+,\s*\d+,\s*NULL,\s*\d+\)\s*=\s*\d+\s*\n`)
-	rxResume := regexp.MustCompile(`<\.\.\. sendfile(64)? resumed> \)\s*=\s*\d+\s*\n`)
+	rx := regexp.MustCompile(`sendfile(64)?\(\d+,\s*\d+,\s*NULL,\s*\d+`)
 	out := buf.String()
-	if !rx.MatchString(out) && !rxResume.MatchString(out) {
+	if !rx.MatchString(out) {
 		t.Errorf("no sendfile system call found in:\n%s", out)
 	}
 }