conflux: Flag set as in full teardown in the free path

We suspect a shutdown race of some sort for which the full teardown is not noticed during the close but should be during the free.

For that, we flag the conflux set as in full teardown (if so) in the free path in case the close path didn't caught it.

Fixes #40870 (closed)

Signed-off-by: David Goulet dgoulet@torproject.org