test: Remove nc.py

The nc.py script is only used in a single test, and for waiting for a
TCP port to be opened for listening.

This patch replaces it entirely, by using chamuyero for the test, and
bash for waiting on a TCP port.

test/t-05-null_address/sendmail.cmy

@@ -0,0 +1,23 @@
+
+c tcp_connect localhost:1025
+
+c <~ 220
+c -> EHLO localhost
+c <... 250 HELP
+c -> MAIL FROM: <>
+c <~ 250
+c -> RCPT TO: user@testserver
+c <~ 250
+c -> DATA
+c <~ 354
+c -> From: Mailer daemon <somewhere@horns.com>
+c -> Subject: I've come to haunt you
+c -> 
+c -> Muahahahaha
+c -> 
+c -> 
+c -> .
+c <~ 250
+c -> QUIT
+c <~ 221
+