Remove calls to policy.check from plugin logic

Remove calls to policy.check from plugin logic

Blueprint make-authz-orthogonal

This patch implements part #3 of this blueprint, according to its
specification.
It does so by allowing the view generator in the API layer to strip
off fields which do not satify authorization policies.
Also, some checks in unit tests for plugins relied on the
capability of the plugin to invoke directly the policy engine.
This checks have been removed and replaced by equivalent unit tests.
Finally, this patch required changes to most test cases for API
extensions in order to ensure the resource attribute map was
updated with the extension's attributes

Change-Id: I1ef94a8a628d34697254b68d7a539bd1c636876e