bug: tar: is not namespace aware

[mkunz7]

Describe your environment

1. minimega version - latest
2. Linux distro/version - ubuntu 18.04 server
3. Go compiler version - 1.12.15
4. VM types - container

Describe the bug
Containers aren't properly transferred and untar'd in a namespace and on launch will only create containers on one node in the namespace.

To Reproduce
Steps to reproduce the behavior:
Start mini on multiple nodes

ns add-hosts all
clear vm config
vm config filesystem tar:container.tar.gz
vm launch container 10
vm start all

Expected behavior
Steps to reproduce should should transfer, extract, and boot