Misc Minor Fixes for Storage Policies

- fixed issue in proxy container POST similar to recent PUT fix (if condition not correct for INT)
- coorected a few test cases using PUT instead of POST
- added missing test for convert_policy_to_index in ContainerController
- added test to provide coverage for maksing sure policy is correctly added to back end headers
(adds coverage for recent if INT condition issues in container PUT/POST for policy 0)

Change-Id: Ifcdf26321491ed2455bbc03636e4b1b318b7d299
Implements: blueprint swift-ec