[FramworkBundle][HttpKernel] Check event listener services are not abstract
bug #9214 [FramworkBundle] Check event listener services are not abstract (lyrixx)

This PR was merged into the 2.2 branch.

Discussion
----------

[FramworkBundle] Check event listener services are not abstract

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |

Commits
-------

6744ead [FramworkBundle][HttpKernel] Check event listener services are not abstract