pthreadpool: we need to use pthreadpool_tevent_per_thread_cwd() on the callers pool

pthreadpool: we need to use pthreadpool_tevent_per_thread_cwd() on the callers pool

In pthreadpool_tevent_job_send() we remember if the job will be chdir
safe. It means we means we need to ask the callers pool when calling
pthreadpool_tevent_per_thread_cwd(), as the callers pool might
be a wrapper using pthreadpool_tevent_force_per_thread_cwd().

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>