Add some v2 flavor_manage API tests

On most APIs, the unit test coverage of v3 is better than the one of v2.
This patch ports v3 flavor_manage API tests to v2 tests for improving v2
API tests.

Change-Id: Ic52b68ea864ba9c4649fe22a431e5e55e72141c5
Treat instance like an object in _start_building

The _start_building method gets an instance object
but was treating it like a dict, so this change
uses dot notation on the instance object fields.

Adds a unit test since this method wasn't directly
unit tested before.

Part of blueprint compute-manager-objects-juno

Change-Id: I8d6b23c70e82fbc7740f3d6af1362905b895addb
Treat instance like an object in _prebuild_instance

The _prebuild_instance method is given an instance object
but was treating it like a primitive dict, so this change
uses dot notation to enforce the object usage.

Adds unit tests since this wasn't directly unit tested
before.

Part of blueprint compute-manager-objects-juno

Change-Id: Id22eb46ed3b4bd8fb48189a40f9df9bb114cd3d4
Report all objects with hash mismatches in a single go

The object hash test previously stopped when it hit the first object with
a mismatched hash. This meant that if you changed a couple objects, you
had to run the test, fix the first, run the test, fix the next, etc.
This patch collects all the data and then asserts the delta set, if
there were mismatches.

Change-Id: Ie35a4dbd6941a1f31e0cef7ea56fa2cc5e9a8ef0
Merge "Treat instance like an object in _start_building"
Merge "Add some v2 flavor_manage API tests"
Merge "Treat instance like an object in _prebuild_instance"
Merge "Report all objects with hash mismatches in a single go"