Add support for sub-interfaces in network_helper::get_interface_ip_networks

[stormshield-gwendald]

getifaddrs in get_interface_ip_networks will return sub-interfaces with the format <interface name>:<interface index>, but this sub-interfaces are not presented in /sys/class/net/, so this sub-interfaces are skipped in refresh_networks_addresses.

This PR fix this by overriding the sub-interfaces name with their parents interfaces name in get_interface_ip_networks.

[GuillaumeGomez]

Nice, thanks!