Fix/Post 1.1.3 test adjustments

[jooname]

• Fixed issue in one of the module unit tests caused by changes done in recent release
• For now removing domain manager usage from one of the integration test fixtures, since to do this properly we need to create a rollback for this fixture and whatever other fixtures are using it. After all app/etc/env.php changes are not reverted automatically and changes to it will be validated after running tests, causing the running of test to be halted.
• Updated sales rule fixtures for integration tests to use the AbstractModel save method, as on Commerce indexer logic is tied to save events of AbstractModel rather than resource model
• Updated one of the product fixtures to grab the saved product instance, as it seems on Commerce the option saving doesn't result in the given product instance being updated, which results in the following fixture code breaking
• Added some new integration test fixtures and also rollbacks in case the tests need to be done without database isolation