PHP-FPM optimizations: send response to user and continue processing shutdown operations (same as it is in mod_php - cache get's written after the request is finished for the user and closed)

git-svn-id: http://www.pimcore.org/svn/pimcore/private/core/trunk@5209 1f8fe7d8-47f0-464c-8d0a-336f4953ab05