Add placement strategies to service definitions.

[MikeTheCanuck]

This is a partial improvement, to be followed with min/max improvements that will improve the robustness even further.

[MikeTheCanuck]

This change will fail for non-god users who attempt to push.

When this change is attempted by god user (@DingoEatingFuzz ) we still end up with this indecipherable failure:

Embedded stack arn:aws:cloudformation:us-west-2:845828040396:stack/hacko-integration-transportService-67KME5SFWBJO/703f8450-0c4f-11e7-b08d-503aca41a029 was not successfully updated. Currently in UPDATE_ROLLBACK_IN_PROGRESS with reason: The following resource(s) failed to update: [Service].

In examining the commits to that service's service.yaml, there is nothing I can see in the last couple of changes that would account for this problem. Nor do I see anything in the transportService block that looks any different than any other 2017 API service.

I'm stumped why the changeset is failing on one of the services that wasn't changed.