iv_work: Shutdown race condition fix.
iv_work: Shutdown race condition fix.

When shutting down a worker thread in response to the thread pool
having been put, execute the ->thread_stop() callback before the
private pool data is free()d.

Signed-off-by: Lennert Buytenhek <8858498612e3a522354216649776e3032dcb7e5b@wantstofly.org>

buytenh/ivykis,buytenh/ivykis