Revert "ssh: add support for banners"

This reverts commit ed5229da99.

Reason for revert: missing language tag in banner message breaks auth against other implementations.

Change-Id: I18ac5b3fe3b4693688b82ff4b0db02dab739c45b
Reviewed-on: https://go-review.googlesource.com/72381
Reviewed-by: Han-Wen Nienhuys <hanwen@google.com>
Run-TryBot: Han-Wen Nienhuys <hanwen@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

ssh/client_test.go

@@ -79,40 +79,3 @@ func TestHostKeyCheck(t *testing.T) {
 		}
 	}
 }
-func TestBannerCallback(t *testing.T) {
-	c1, c2, err := netPipe()
-	if err != nil {
-		t.Fatalf("netPipe: %v", err)
-	}
-	defer c1.Close()
-	defer c2.Close()
-
-	serverConf := &ServerConfig{
-		NoClientAuth: true,
-		BannerCallback: func(conn ConnMetadata) string {
-			return "Hello World"
-		},
-	}
-	serverConf.AddHostKey(testSigners["rsa"])
-	go NewServerConn(c1, serverConf)
-
-	var receivedBanner string
-	clientConf := ClientConfig{
-		User:            "user",
-		HostKeyCallback: InsecureIgnoreHostKey(),
-		BannerCallback: func(message string) error {
-			receivedBanner = message
-			return nil
-		},
-	}
-
-	_, _, _, err = NewClientConn(c2, "", &clientConf)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	expected := "Hello World"
-	if receivedBanner != expected {
-		t.Fatalf("got %s; want %s", receivedBanner, expected)
-	}
-}