talloc: use atexit() again instead of a library destructor

talloc: use atexit() again instead of a library destructor

The change for https://bugzilla.samba.org/show_bug.cgi?id=7587
("talloc_autofree_context() in shared libraries and plugins is a bad idea on FreeBSD")
(ommit 41b6810ba01f44537f470c806adb8686e1a39c48)
causes the following for sssd on Linux:

     Stack trace of thread 19667:
     #0  0x00007f2cab91ff6b __GI_raise (libc.so.6)
     #1  0x00007f2cab90a5c1 __GI_abort (libc.so.6)
     #2  0x00007f2cab90a491 __assert_fail_base (libc.so.6)
     #3  0x00007f2cab9186e2 __GI___assert_fail (libc.so.6)
     #4  0x00007f2cb10aaca5 k5_mutex_lock (libkrb5.so.3)
     #5  0x00007f2cb10ab790 k5_mutex_lock (libkrb5.so.3)
     #6  0x00007f2cb10ab8f5 profile_free_file (libkrb5.so.3)
     #7  0x00007f2cb10ab983 profile_close_file (libkrb5.so.3)
     #8  0x00007f2cb10af249 profile_release (libkrb5.so.3)
     #9  0x00007f2cb10a06c7 k5_os_free_context (libkrb5.so.3)
     #10 0x00007f2cb1075a9a krb5_free_context (libkrb5.so.3)
     #11 0x000055cea7cb2dd1 kcm_data_destructor (sssd_kcm)
     #12 0x00007f2cac153e96 _tc_free_internal (libtalloc.so.2)
     #13 0x00007f2cac1537b0 _tc_free_internal (libtalloc.so.2)
     #14 0x00007f2cac1537b0 _tc_free_internal (libtalloc.so.2)
     #15 0x00007f2cac1537b0 _tc_free_internal (libtalloc.so.2)
     #16 0x00007f2cac1537b0 _tc_free_internal (libtalloc.so.2)
     #17 0x00007f2cac14e648 _talloc_free (libtalloc.so.2)
     #18 0x00007f2cac14c480 talloc_lib_fini (libtalloc.so.2)
     #19 0x00007f2cb151da96 _dl_fini (ld-linux-x86-64.so.2)
     #20 0x00007f2cab9226bc __run_exit_handlers (libc.so.6)
     #21 0x00007f2cab9227ec __GI_exit (libc.so.6)
     #22 0x00007f2cb030dc61 orderly_shutdown (libsss_util.so)
     #23 0x00007f2cac365a46 tevent_common_check_signal (libtevent.so.0)
     #24 0x00007f2cac367975 epoll_event_loop_once (libtevent.so.0)
     #25 0x00007f2cac365dab std_event_loop_once (libtevent.so.0)
     #26 0x00007f2cac362098 _tevent_loop_once (libtevent.so.0)
     #27 0x00007f2cac3622eb tevent_common_loop_wait (libtevent.so.0)
     #28 0x00007f2cac365d3b std_event_loop_wait (libtevent.so.0)
     #29 0x00007f2cb030eb37 server_loop (libsss_util.so)
     #30 0x000055cea7cb29f4 main (sssd_kcm)
     #31 0x00007f2cab90c1eb __libc_start_main (libc.so.6)
     #32 0x000055cea7cb2c7a _start (sssd_kcm)

We still only register one atexit handler instead of multiple ones
like in talloc 2.1.11, but avoids using a library destructor.

Bug #7587 seems to be fixed by not using talloc_autofree_context()
within samba.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13366

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andreas Schneider <asn@samba.org>