s3: smbd: Tear down global_smbXsrv_client in the correct order.

s3: smbd: Tear down global_smbXsrv_client in the correct order.

The talloc heirarchy looks like this:

global_smbXsrv_client
    |                 |
    V                 V
    session_table    sconn
       |
       V
      session (destructor references global_smbXsrv_client->sconn)

So don't free global_smbXsrv_client->sconn before the
session destructor fires.

------------------------------------------------
6 <signal handler called>
7 0x00007f47ba82da1a in file_close_user (sconn=0x0, vuid=1584077283) at ../source3/smbd/files.c:250
8 0x00007f47ba922a74 in smbXsrv_session_logoff (session=0x7f47be8bbf80) at ../source3/smbd/smbXsrv_session.c:1404
9 0x00007f47ba921912 in smbXsrv_session_destructor (session=0x7f47be8bbf80) at ../source3/smbd/smbXsrv_session.c:1068
10 0x00007f47b784e2fc in _talloc_free_internal () from /usr/lib/libtalloc.so.2
11 0x00007f47b784f495 in _talloc_free_children_internal () from /usr/lib/libtalloc.so.2
12 0x00007f47b784e49f in _talloc_free_internal () from /usr/lib/libtalloc.so.2
13 0x00007f47b784f495 in _talloc_free_children_internal () from /usr/lib/libtalloc.so.2
14 0x00007f47b784e49f in _talloc_free_internal () from /usr/lib/libtalloc.so.2
15 0x00007f47b784f88e in _talloc_free () from /usr/lib/libtalloc.so.2
16 0x00007f47ba92b2f1 in exit_server_common (how=SERVER_EXIT_NORMAL, reason=0x0) at ../source3/smbd/server_exit.c:234
------------------------------------------------

BUG: https://bugzilla.samba.org/show_bug.cgi?id=11375

Signed-off-by: Jeremy Allison <jra@samba.org>
Reviewed-by: Stefan Metzmacher <metze@samba.org>
Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Wed Nov 25 03:40:46 CET 2015 on sn-devel-104