NetworkPkg: Remove ASSERT and use error handling in IpSecDxe

NetworkPkg: Remove ASSERT and use error handling in IpSecDxe

This patch is used to refine the code by removing ASSERT and
using error handling in IpSecDxe driver.

Cc: Ye Ting <ting.ye@intel.com>
Cc: Fu Siyuan <siyuan.fu@intel.com>
Cc: Zhang Lubo <lubo.zhang@intel.com>
Cc: Yao Jiewen <jiewen.yao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jiaxin Wu <jiaxin.wu@intel.com>
Reviewed-by: Ye Ting <ting.ye@intel.com>