r13606: An attempt to fix #3525.

r13606: An attempt to fix #3525.

The problem was that the supportedControls were being stolen into the
result sent to the client, then talloc_free()ed.  This caused them to
be invalid on the next rootDSE query.

This also tries to avoid attaching the result to the long-term samdb
context, and avoids an extra loop in the result processing (pointed
out by tridge).

Andrew BARtlett