nas_config(): provide entire IP address to configure

Prior to this commit, there was a global variable baseNetAddress that
could be set independently through a setter and also through the
configuration module. This baseNetAddress (16 bits IPv4) would then be
complemented with two more bytes in nas_config().

However, this is counter-productive, as not only we have a global
variable that is avoidable (we can give the entire address to
nas_config() directly), but it also would not work with IPv6. Hence,
modify to give nas_config() the entire address. A follow-up commit will
add IPv6 support.