Fix access to auto-generated socket paths

[svirt]

Adding support for https://bugzilla.redhat.com/show_bug.cgi?id=1146886

(libvirt commits f1f68ca33433825ce0deed2d96f1990200bc6618, f674dc6794e0946f89313f477aa7886a4a28188e)

Abstract from the libvirt commit:

"qemu: Fix access to auto-generated socket paths

We are automatically generating some socket paths for domains, but all those paths end up in a directory that's the same for multiple domains. The problem is that multiple domains can each run with different seclabels (users, selinux contexts, etc.). The idea here is to create a per-domain directory labelled in a way that each domain can access its own unix sockets."

[lmr]

Hi @svirt. As you might know, we're moving virt-test to avocado-vt, so I please ask you to consider re-implementing this functionality in the later. The new repo is:

https://github.com/avocado-framework/avocado-vt

Please keep in mind the following guidelines when creating the new PR:

1) Most of the time you can pick the patches of your original PR and merge them on a new branch with minimal changes. 3) Don't use autotest APIs, since we're moving away from using them. Please review the code and change things like utils.system -> process.system, utils.run -> process.run, so on and so forth.

Thanks, and I'm sorry for any inconveniences we might have caused your team.