Renable tests in CI

[zeenix]

This is a follow-up from discussion here.

It'd be really awesome if PR got properly tested through running tests. I understood that they were disabled because of libvirt setup being difficult in travis. I believe it'll be much simpler if tests used session libvirt connection that doesn't require much setup (if any).

The only issue I foresee is the network tests. We'll have to disable most (all?) of them. But running all other tests against PRs would already be a big win and IMO this issue shouldn't block us from reenabling tests in CI.