Revert "crypto/tls: don't send IP literals as SNI values."

This reverts commit a4dcc69201.

Change-Id: Ib55fd349a604d6b5220dac20327501e1ce46b962
Reviewed-on: https://go-review.googlesource.com/16770
Reviewed-by: Adam Langley <agl@golang.org>

src/crypto/tls/handshake_client.go

@@ -49,20 +49,13 @@ func (c *Conn) clientHandshake() error {
 		return errors.New("tls: NextProtos values too large")
 	}
 
-	sni := c.config.ServerName
-	// IP address literals are not permitted as SNI values. See
-	// https://tools.ietf.org/html/rfc6066#section-3.
-	if net.ParseIP(sni) != nil {
-		sni = ""
-	}
-
 	hello := &clientHelloMsg{
 		vers:                c.config.maxVersion(),
 		compressionMethods:  []uint8{compressionNone},
 		random:              make([]byte, 32),
 		ocspStapling:        true,
 		scts:                true,
-		serverName:          sni,
+		serverName:          c.config.ServerName,
 		supportedCurves:     c.config.curvePreferences(),
 		supportedPoints:     []uint8{pointFormatUncompressed},
 		nextProtoNeg:        len(c.config.NextProtos) > 0,