[HttpFoundation] [Request] fix baseUrl parsing to fix wrong path_info

This is the symfony 2.7 branch fix for the issue described in #13038 and #13039 

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #13038 
| License       | MIT

[HttpFoundation] [Request]
* added missing slash to baseUrl-path part check to remove the path, only when it's also a path in the uri
[HttpFoundation] [Tests] [RequestTest]
* fixed and added unittests

Happy christmas!