Add API tests for portgroup update

Add tests:
  test_update_portgroup_replace,
  test_update_portgroup_remove_by_key,
  test_update_portgroup_remove_collection,
  test_update_portgroup_add,
  test_update_portgroup_mixed_ops.

Change-Id: I2dfc9549ad4bda14ff23b6bfef748fe185c9a657
2 files changed