spec: If installing default network, restart libvirtd
    
    If libvirt-daemon-config-network is installed while libvirtd is already
    running, the daemon doesn't notice the network. Users then have to
    manually restart libvirtd (or reboot) to pick up the network.
    
    Instead let's trigger a daemon restart when the package is first installed.
    Then the default network is available immediately if libvirtd was already
    running.
    
    https://bugzilla.redhat.com/show_bug.cgi?id=867546