nixos/tests/virtualbox: Fix netcat invocation

This is a backwards-incompatibility in netcat-openbsd introduced due to
bumping the netcat version to 1.130 in
a72ba66.

Version 1.130 no longer exits on EOF but now needs to be passed the -N
flag in order to exit on EOF.

The upstream change reads[1] like this:

  Don't shutdown nc(1)'s network socket when stdin closes. Matches
  *Hobbit*'s original netcat and GNU netcat; revert to old behaviour
  with the new -N flag if needed. After much discussion with otto
  deraadt tedu and Martin Pelikan.  ok deraadt@

Here is the diff of this change:

http://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/nc/netcat.c.diff?r1=1.110&r2=1.111&f=h

[1]: http://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/nc/netcat.c?rev=1.111&content-type=text/x-cvsweb-markup

Signed-off-by: aszlig <aszlig@redmoonstudios.org>

nixos/tests/virtualbox.nix

@@ -461,11 +461,11 @@ in mapAttrs mkVBoxTest {
     my $test1IP = waitForIP_test1 1;
     my $test2IP = waitForIP_test2 1;
 
-    $machine->succeed("echo '$test2IP' | nc '$test1IP' 1234");
-    $machine->succeed("echo '$test1IP' | nc '$test2IP' 1234");
+    $machine->succeed("echo '$test2IP' | nc -N '$test1IP' 1234");
+    $machine->succeed("echo '$test1IP' | nc -N '$test2IP' 1234");
 
-    $machine->waitUntilSucceeds("nc '$test1IP' 5678 >&2");
-    $machine->waitUntilSucceeds("nc '$test2IP' 5678 >&2");
+    $machine->waitUntilSucceeds("nc -N '$test1IP' 5678 < /dev/null >&2");
+    $machine->waitUntilSucceeds("nc -N '$test2IP' 5678 < /dev/null >&2");
 
     shutdownVM_test1;
     shutdownVM_test2;