Fix qos api-tests after policy changes

Fix qos api-tests after policy changes

The policy.json update in change
Ide1cd30979f99612fe89dddf3dc0e029d3f4d34a breaks the qos api-tests
due to actions which the default policy won't allow, like qos
rules or policies creation by non-admins.

We removed test_rule_association_nonshared_policy which
is not possible with the default policy.json in favor of
test_policy_create_forbidden_for_regular_tenants.

This commit unblocks the qos api-test re-enablement.

Partially-Implements: blueprint quantum-qos-api

Change-Id: Ib77412bd95ad5b65ad0f6964d9809b5f707847f5