[Libvir] testing libvirtd: don't hard-code $HOME/.libvirt/libvirt-sock

I've written a test to exercise libvirtd a little. Unfortunately, if I'm already running libvirtd, that test fails and I can't do anything about it: $ ./libvirtd & ./libvirtd Failed to bind socket to '(a)/j/.libvirt/libvirt-sock': Address already in use [Exit 2] Any objection to providing an option to libvirtd that specifies that directory (also used to form server->logDir)? It feels like it should come from the config file, but I haven't looked at details yet.