util: API to detect if libvirt bridge net is available
util: API to detect if libvirt bridge net is available

We do this by checking if:

* System libvirtd is running
* Qemu is allowed to run a helper to access bridge net.
  WARNING: We only look at a hardcoded path currently so it will fail for
  qemu installed in custom prefix.

https://bugzilla.gnome.org/show_bug.cgi?id=677688

vbenes/gnome-boxes,vbenes/gnome-boxes