* gnu/services/virtualization.scm (%libvirt-activation): Activate
default libvirt network configuration file.
* gnu/tests/virtualization.scm (run-libvirt-test): Drop network
definition test and replace it with a test checking that the default
network is inactive by default.
Change-Id: I03b6314a390c6d93ebf886d7033867ff5cacad74