tests: Make the qemu logs persistent
tests: Make the qemu logs persistent

I'd like to consume these logs in talks and discussions about our
setup. These show the number of VMs that were launched, which operating
systems, on which hosts, and for how long they ran.

I would like to gather these for many months without cleaning up the
data.

Closes #140
stefwalter/cockpituous,cockpit-project/cockpituous,stefwalter/cockpituous,cockpit-project/cockpituous