s3: Fix a memory leak in check_sam_security_info3

s3: Fix a memory leak in check_sam_security_info3

Abartlet, this commit makes check_sam_security_info3 use talloc_tos() and also
cleans up the temporary talloc stackframe.

The old code created a temporary talloc context off "mem_ctx" but failed to
clean up the tmp_ctx in all but one return paths.

talloc_stackframe()/talloc_tos() is designed as a defense against exactly this
error: Even if we failed to free the frame when returning from the routine, it
would be cleaned up very soon, in our main event loop.

Please check this patch!

Thanks,

Volker

Autobuild-User: Volker Lendecke <vlendec@samba.org>
Autobuild-Date: Sat Mar  5 14:08:37 CET 2011 on sn-devel-104