Add an echo client to be used instead of nc.

nc behaviour depends on the implementation version of what's on the current host.
Here we use our own client with stable behaviour.

Signed-off-by: Federico Paolinelli <fpaoline@redhat.com>

pkg/testutils/echo/server/main.go

@@ -0,0 +1,57 @@
+// Echosvr is a simple TCP echo server
+//
+// It prints its listen address on stdout
+//    127.0.0.1:xxxxx
+//  A test should wait for this line, parse it
+//  and may then attempt to connect.
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"net"
+	"os"
+	"strings"
+	"time"
+)
+
+func main() {
+	listener, err := net.Listen("tcp", ":")
+	if err != nil {
+		panic(err)
+	}
+	_, port, err := net.SplitHostPort(listener.Addr().String())
+	if err != nil {
+		panic(err)
+	}
+	fmt.Printf("127.0.0.1:%s\n", port)
+	for {
+		conn, err := listener.Accept()
+		if err != nil {
+			panic(err)
+		}
+		go handleConnection(conn)
+	}
+}
+
+func handleConnection(conn net.Conn) {
+	conn.SetReadDeadline(time.Now().Add(1 * time.Minute))
+	content, err := bufio.NewReader(conn).ReadString('\n')
+	if err != nil && err != io.EOF {
+		fmt.Fprint(os.Stderr, err.Error())
+		return
+	}
+
+	conn.SetWriteDeadline(time.Now().Add(1 * time.Minute))
+	if _, err = conn.Write([]byte(strings.TrimSuffix(content, "\n"))); err != nil {
+		fmt.Fprint(os.Stderr, err.Error())
+		return
+	}
+
+	if err = conn.Close(); err != nil {
+		fmt.Fprint(os.Stderr, err.Error())
+		return
+	}
+
+}