Fixed products being removed when canceling subscriptions
Fixed products being removed when canceling subscriptions

refs https://github.com/TryGhost/Team/issues/748

Previously when a change happened to a subscription the member's
products would be reset purely based on the subscriptions. Since we now
support setting products outside of subscriptions, we must make sure
than a change to a subscription will only affect the product for which
the subscription was for

TryGhost/Ghost,TryGhost/Ghost,TryGhost/Ghost