pwrap: Set up a pthread_atfork() handler to not delete or config directory

pwrap: Set up a pthread_atfork() handler to not delete or config directory

Python3 has some strange behavior. It forks a child which then exits.
This child calls the destructor which deletes our /tmp/pam.X directory.

As we later try to bind the symbol the directory is gone and we detected
and error which results in exit(-1).

Signed-off-by: Andreas Schneider <asn@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>