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>