make check: relying on /tmp/cni/* is not sustainable

[grahamwhaley]

Currently, in order to run 'make check' you must have run:
https://github.com/containers/virtcontainers/blob/master/utils/virtcontainers-setup.sh
and subsequently have some files installed in /tmp/cni/*.

This is not sustainable. A simple machine reboot will remove all of /tmp, and stop your make check from working.

Better maybe would be to install those files into a tmp subdir of the repo directory itself, which at least then will not magically disappear.

thoughts?