os: disable symlink tests on android.

Creating symlinks (/data/local/tmp/*) doesn't seem to work
on android-L (tested on nexus5). I cannot find any official
documentation yet but just guess it's a measure for security
attacks using symlinks.

The tests failed with 'permission denied' errors.

For golang/go#10807

Change-Id: I99a9c401c6ecca3c4adc7b21708adaf3dd601279
Reviewed-on: https://go-review.googlesource.com/16115Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/os/os_test.go

@@ -672,7 +672,7 @@ func TestSymlink(t *testing.T) {
 
 func TestLongSymlink(t *testing.T) {
 	switch runtime.GOOS {
-	case "plan9", "nacl":
+	case "android", "plan9", "nacl":
 		t.Skipf("skipping on %s", runtime.GOOS)
 	case "windows":
 		if !supportsSymlinks {

src/os/path_test.go

@@ -170,7 +170,7 @@ func TestRemoveAll(t *testing.T) {
 
 func TestMkdirAllWithSymlink(t *testing.T) {
 	switch runtime.GOOS {
-	case "nacl", "plan9":
+	case "android", "nacl", "plan9":
 		t.Skipf("skipping on %s", runtime.GOOS)
 	case "windows":
 		if !supportsSymlinks {