Take the libvirt RPM and split it into three pieces

 - libvirt-daemon - libvirtd & other mandatory bits for its operation
 - libvirt-daemon-config-network - the virbr0 config definition
 - libvirt-daemon-config-nwfilter - the firewall config rules

For backwards compatibility with existing installs / application RPM
deps, the 'libvirt' RPM is retained, but will have a dependency on
the 3 new RPMs.