Use nameserverdata prop when available

I get some invalid IPv4 Nameservers in plasma-nm.

I believe this is because the nameservers property in NetworkManager DBus is deprecated as stated in https://developer-old.gnome.org/NetworkManager/stable/gdbus-org.freedesktop.NetworkManager.IP4Config.html#gdbus-property-org-freedesktop-NetworkManager-IP4Config.Nameservers the nameserverData property is preferred. This also gives me the correct nameservers used by NetworkManager.

This Merge Request prioritizes nameserverData if available. Else it falls back to nameserver

This is an example. I did not set that IPv4 Primary Nameserver. It gets it while converting to higher byte order in the function ntohl()