Port EMC VNX CLI to Python 3

Port EMC VNX CLI to Python 3

CreateConsistencyGroupTask, WaitMigrationsCompleteTask: sort the lun
identifier keys to have a determinist order. On Python 3, the hash
function is randomized, so set() order is undefined and changes at
each run.

Other changes:

* Replace map() with list-comprehension to get a list on Python 3.
* Replace assertTrue(str.find(pattern) > 0) with
  assertIn(pattern, str) to not fail if pattern is at the beginning
  on the string. On Python 3, the hash function is randomized and so
  parts of the provider_location are in a random order, it can be at
  the beginning.
* tests-py3.txt: add cinder.tests.unit.test_emc_vnxdirect

Partial-Implements: blueprint cinder-python3
Change-Id: I114029c1c9862583e64781379001870a682ea42d