spec: Restart libvirtd in posttrans
    
    When upgrading libvirt packages, there's no strict ordering for the
    installation or removal of the individual libvirt sub packages. Thus
    libvirt-daemon may be upgraded (and its %postun scriptlet) started
    before all sub packages with driver libraries are upgraded. When
    libvirt-daemon's %postun scriptlet restarts the daemon old drivers may
    still be laying around and the daemon may crash when it tries to use
    them.
    
    Let's restart the daemon in %posttrans to make sure libvirtd is
    restarted only after all sub packages are at the same version.
    
    https://bugzilla.redhat.com/show_bug.cgi?id=1464300
    
    Signed-off-by: Jiri Denemark <jdenemar@redhat.com>