Remove unused function ni_local_socket_listen()

This function goes back to the early days of wicked when it was
using a REST interface served via an AF_LOCAL socket. This stuff
has been for a few years, so it's time to say goodbye to some of
its supporting functions.

Signed-off-by: Olaf Kirch <okir@suse.de>
Remove unused function ni_local_socket_connect

This function goes back to the early days of wicked when it was
using a REST interface served via an AF_LOCAL socket. This stuff
has been for a few years, so it's time to say goodbye to some of
its supporting functions.

Signed-off-by: Olaf Kirch <okir@suse.de>
Remove unused function ni_local_socket_pair

This function goes back to the early days of wicked when it was
using a REST interface served via an AF_LOCAL socket. This stuff
has been for a few years, so it's time to say goodbye to some of
its supporting functions.

Signed-off-by: Olaf Kirch <okir@suse.de>
Add comment/caveat to __ni_process_output_recv

The socket recv buffer can grow without bounds here. No immediate idea
what to do about this, but flag this as a potential source of trouble.

Signed-off-by: Olaf Kirch <okir@suse.de>
ni_config_t: remove recv_max member

This member variable was used by ni_local_socket_listen(), which is gone
now.

Signed-off-by: Olaf Kirch <okir@suse.de>
Merge pull request #410 from okirch/nuke-obsolete-socket-fncts