also consider alias in Container::has()
merged branch lsmith77/container_check_alias_in_has_method (PR #8252)

This PR was merged into the 2.3 branch.

Discussion
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Container check alias in has method

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | [![Build Status](https://travis-ci.org/lsmith77/symfony.png?branch=container_check_alias_in_has_method)](https://travis-ci.org/lsmith77/symfony)
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

This bug might also be in 2.2 but we encountered it in 2.3 and the relevant code was changed slightly from 2.2 to 2.3. We noticed this issue here:
https://github.com/symfony-cmf/RoutingBundle/issues/109

The issue is caused by the ``$container->has->('router')`` check in the Router related commands:
https://github.com/symfony/FrameworkBundle/blob/master/Command/RouterDebugCommand.php#L32

As with the CMF we use a chain router service that is aliased to ``router``, the commands do not get registered.

One could classify this as a BC break, but imho its a bug fix.

Commits
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aa79393 also consider alias in Container::has()