[HttpKernel] Remove conflicting `use` from `NullLogger`
merged branch stloyd/bugfix/nulllogger (PR #6704)

This PR was merged into the master branch.

Commits
-------

eb0d2ab [HttpKernel] Remove conflicting `use` from `NullLogger`

Discussion
----------

[HttpKernel] Remove conflicting `use` from `NullLogger`

Without this code dies with fatal:
> Cannot use Psr\Log\LoggerInterface as LoggerInterface because the name is already in use

---------------------------------------------------------------------------

by Seldaek at 2013-01-11T11:00:50Z

Oops :)