netdev: fix netmask in netdev_get_addrs

netdev: fix netmask in netdev_get_addrs

When iterating on getifaddrs result, ifa_netmask is dereferenced, but it's
already a pointer to struct sockaddr. This would result in wrong masks being
used when comparing addresses while calculating the source address given a
destination address at the routing code.

For example, the mask ::ffff:116.85.0.0 would be used, causing 172.16.100.0/24
to match 172.16.101.1, though they should not match.

This will not happen when using a dummy netdev, as netdev_get_addrs is not used
by it.

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@redhat.com>
Acked-by: Pravin B Shelar <pshelar@ovn.org>