Don't use "Zero-I/O mode" in nc client in the TCP mode

It seems that using "Zero-I/O mode" ("-z" option) in nc client is
necessary for the UDP tests but it is causing failures when it runs it TCP
mode.

Closes: rhbz#2211094
Change-Id: I7d313a7afc60825885854eaa6de858b1f53e5e46
1 file changed