util: Update virNetDevGetIPAddress to get IPv6 addresses

util: Update virNetDevGetIPAddress to get IPv6 addresses

Add static virNetDevGetifaddrsAddress to attempt to get the interface
IP address. If getifaddrs is not supported, fall back to
virNetDevGetIPv4AddressIoctl to get the IP address.

This allows IPv6 addresses to be used for <listen type='network>
with device-backed networks.

https://bugzilla.redhat.com/show_bug.cgi?id=1192318

Signed-off-by: Luyao Huang <lhuang@redhat.com>
Signed-off-by: John Ferlan <jferlan@redhat.com>
Signed-off-by: Ján Tomko <jtomko@redhat.com>