MdeModulePkg: Do not use hard coded TTL/ToS in PXE driver.

EFI_PXE_BASE_CODE_PROTOCOL has interface to set the TTL and ToS value, but
not used by the UdpWrite() interface. The code always use a hard coded 16
for the TTL and 0 for ToS.
This patch update the UpdWrite() to use the TTL and ToS which have been set
by the SetParameters().

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Fu Siyuan <siyuan.fu@intel.com>
Reviewed-By: Wu Jiaxin <jiaxin.wu@intel.com>
Reviewed-By: Samer El-Haj-Mahmoud <elhaj@hpe.com>

MdeModulePkg/Universal/Network/UefiPxeBcDxe/PxeBcImpl.c

@@ -1,7 +1,7 @@
 /** @file
   Interface routines for PxeBc.
 
-Copyright (c) 2007 - 2015, Intel Corporation. All rights reserved.<BR>
+Copyright (c) 2007 - 2016, Intel Corporation. All rights reserved.<BR>
 This program and the accompanying materials
 are licensed and made available under the terms and conditions of the BSD License
 which accompanies this distribution.  The full text of the license may be found at
@@ -1435,7 +1435,9 @@ EfiPxeBcUdpWrite (
              &Private->StationIp.v4,
              &Private->SubnetMask.v4,
              &Private->GatewayIp.v4,
-             &Private->CurrentUdpSrcPort
+             &Private->CurrentUdpSrcPort,
+             Private->Mode.TTL,
+             Private->Mode.ToS
              );
   if (EFI_ERROR (Status)) {
     Private->CurrentUdpSrcPort = 0;