Added policy check for backup operations

This patch adds policy checks for operations in the backup extension
consisting of create, delete, restore, get and get_all.  It also adds
policies into the policy.json files in the tests and etc directories.

Fixes Bug: 1188386

Change-Id: I847640051c5d25cebf06b8658b27d4b82603d796
Merge "Added policy check for backup operations"