zookepeer should not write JNA libraries to /tmp
By default the JNA tmpdir is set to /tmp. This conflicts with some standard security policies that dictate that /tmp should be mounted as noexec.
My first thought is to use /run, but that is mounted noexec by default on Ubuntu 16.04 LTS, too.
We should set the JNA tmpdir to somewhere we control: /var/lib/dcos/exhibitor/tmp seems like a good option.