Fix instance actions testing

Somehow, the instance actions API was different in three places:

1. The actual API from a running system
2. The regular unit tests
3. The api_samples tests

This fixes the fake_instance_actions module to look like the database
model (which was the root of the problem) as well as the api_samples
and regular unit tests to properly confirm the actual behavior I
validated manually against a running system. This looks like it
changes the external API, but in fact, it makes things match what
the external API actually is.

Change-Id: I0c8ddff3e0819a65667617083dfaa74f7317cc05
Merge "Fix instance actions testing"