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
(cherry picked from commit 1d440008)