flatpak: Update to libvirt 4.7.0
4.7 fixes the following security issues: https://security.libvirt.org/2018/0004.html https://security.libvirt.org/2018/0005.html
This also makes libvirt buildable against glibc 2.28
4.7 fixes the following security issues: https://security.libvirt.org/2018/0004.html https://security.libvirt.org/2018/0005.html
This also makes libvirt buildable against glibc 2.28