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

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>