NetworkPkg: 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>

NetworkPkg/UefiPxeBcDxe/PxeBcImpl.c

@@ -1,7 +1,7 @@
 /** @file
   This implementation of EFI_PXE_BASE_CODE_PROTOCOL and EFI_LOAD_FILE_PROTOCOL.
 
-  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
@@ -1125,7 +1125,9 @@ EfiPxeBcUdpWrite (
                &Private->SubnetMask.v4,
                &Private->GatewayIp.v4,
                &Private->CurSrcPort,
-               DoNotFragment
+               DoNotFragment,
+               Private->Mode.TTL,
+               Private->Mode.ToS
                );
   }