net: skip TestSendfileParts on dragonfly and solaris

Skip it like on freebsd until there is proper a fix for #25809

Updates #25809

Change-Id: Id53c433aee75f2a992ab6a8d58d98fd1f8a6c1c6
Reviewed-on: https://go-review.googlesource.com/117698
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>

src/net/sendfile_test.go

@@ -94,7 +94,8 @@ func TestSendfile(t *testing.T) {
 }
 
 func TestSendfileParts(t *testing.T) {
-	if runtime.GOOS == "freebsd" {
+	switch runtime.GOOS {
+	case "dragonfly", "freebsd", "solaris":
 		t.Skipf("skipping on %s (see golang.org/issue/25809 for details)", runtime.GOOS)
 	}