Refactor to 'dict' from 'IterableUserDict' which was only required for old
python interpreter.
Sort imports according to PEP8
Remove those we dont need.
Cc: Bob Feng <bob.c.feng@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Jaben Carsey <jaben.carsey@intel.com>
Reviewed-by: Bob Feng <bob.c.feng@intel.com>