fiber: Move fiber_stack_destroy prior the fiber_stack_create

This will allow us to call it from inside fiber_stack_create
as we need to clean up resources on error.

Part-of #4541

Signed-off-by: Kirill Yukhin <kyukhin@tarantool.org>
(cherry picked from commit 8f1251d3611aa30d5bb6098716e965fd8dc08551)