Revert "zerovm-cli: don't run tests inside LXC"

This reverts commit 9ab7db298ebec21ed69f4618bd386277e71fe391.

This change broke the nightly CI build for zerovm-cli; test reports were
not copied out of the lxc environment and so could not be published.

See http://ci.oslab.cc/job/zerovm-cli/62/.