UPT used to use "B:" as the temp directory which may cause conflict, now it will choose a valid volume. Also UPT now accepts empty sections. Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Hess Chen <hesheng.chen@intel.com> Reviewed-by: Yonghong Zhu <yonghong.zhu@intel.com>