[WIP][Cookbook][Service Container][Scopes] Synchronized Services Setter Injection Does Not Occur When Entering Scope 

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | 2.3+
| Fixed tickets | n/a

My interpretation of the documentation is that synchronized services are injected as dependencies when a given scoped is entered or exited.  My expectation is that the process takes place when [Container::enterScope()](https://github.com/symfony/symfony/blob/master/src/Symfony/Component/DependencyInjection/Container.php#L374) or [Container::leaveScope()](https://github.com/symfony/symfony/blob/master/src/Symfony/Component/DependencyInjection/Container.php#L422) are invoked, however it seems that the setter is called only when the [Container::set()](https://github.com/symfony/symfony/blob/master/src/Symfony/Component/DependencyInjection/Container.php#L211) is invoked, which implies that synchronized services must also be synthetic.