Device setup rework

I experienced some issues trying to run CI test over other vagrant already available boxes... so dug a bit in the network devices setup scripts. I ended up doing light refactoring of few parts and creating a new subfolder to host the scripts used to setup the network devices before the run of the tests, sharing the code for network setup for nmcli and nmtui tests. Not tested the setup for dcb, inf and gsm tests. Note that there are also few fixes for minor bugs preventing correct tests execution.