Change callback handler type to avoid saving PSID info in browser temp buffer. Also clean the buffer after using it. Cc: Feng Tian <feng.tian@intel.com> Reviewed-by: Jiewen Yao <jiewen.yao@intel.com> Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Eric Dong <eric.dong@intel.com>