Port infortrend driver to Python 3

Port infortrend driver to Python 3

* InfortrendCommon: sort dictionary items to get a reliable
  behaviour. On Python 3, the hash function is randomized by default.

  - _get_minimun_mapping_channel_id(): sort LUN mapping by keys
  - _do_fc_connection(): sort initiator_target_map keys

* InfortrendCommon._create_partition_with_pool(): cast gi_to_mi()
  result to int. On Python 3, gi_to_mi() returns a float (a/b always
  return a float, even for int/int).
* test_retype_with_migrate(): build create_params using a dictionary
  to create parameter in the same order than the driver.
* tests-py3.txt: cinder.tests.unit.test_infortrend_common

Change-Id: Idd849a9cd5dc0ad17c5d8d54da489346c018e778