[th/cli-import-dupl-args] nmcli: don't print warning in `nmcli connection import` about duplicate parameters

It seems uncommon that a command line tool warns about duplicate paramters. Usually, the latter just overwrites the former. That is also useful so that you can have for example an alias that sets a default type

  nmcli_import="nmcli connection import type keyfile"

but still call it like

  nmcli_import file $FILE type openvpn

This is a change in behavior. Not only stop we printing a warning, we will now prefer the latter argument. Previously, the first was honored. This change in behavior is a problem, but such uses were warned against in the past, and hopefully nobody did this or relied on this.