Revert "BUG/MINOR: task: Don't defer tasks release when HAProxy is stopping"

Revert "BUG/MINOR: task: Don't defer tasks release when HAProxy is stopping"

This reverts commit d9404b464faae3340ac1745b594929e4b7edd650.

In fact, there is a BUG_ON() in __task_free() function to be sure the task
is no longer in the wait-queue or the run-queue. Because the patch tries to
fix a "leak" on deinit, it is safer to revert it. there is no reason to
introduce potential bug for this kind of issues. And there is no reason to
impact the normal use-cases at runtime with additionnal conditions to only
remove a task on deinit.