Pass object to policy when finding fields to strip

During the evaluation of fields to strip in responses to list
operations, pass also the first object in the list to the
policy engine.
This will avoid errors in policy evaluation if during
an upgrade from icehouse policy.json was not updated to remove
attribute-level policies dependent on resource values.

Closes-Bug: #1323715

Change-Id: Iaa6ed3bbf4a07ce0b614a4197cabdfa1cb36d427
Merge "Pass object to policy when finding fields to strip"