s3-rpc_server/mdssd: use smbd_reinit_after_fork()

s3-rpc_server/mdssd: use smbd_reinit_after_fork()

Using smbd_reinit_after_fork() rather then reinit_after_fork() ensures
am_parent is reset to NULL. Otherwise, when exiting for some reason, the
inherited atexit handler killkids() calls kill(0,SIGTERM) terminating
our whole process group including the main smbd.

Bug: https://bugzilla.samba.org/show_bug.cgi?id=12016

Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>
Autobuild-User(master): Volker Lendecke <vl@samba.org>
Autobuild-Date(master): Mon Jul 11 02:02:33 CEST 2016 on sn-devel-144

(cherry picked from commit 6efd0af5e8d8ee81b5f53afb126d87950088b7cd)