git: openjdk/loom: fibers: Fix issue with not unregistering vthreads when they have exited. They were still appearing in the list of threads given to debuggers.

[duke]

Changeset: 9fd4b017
Author:    Chris Plummer <chris.plummer at oracle.com>
Date:      2021-03-10 03:56:14 +0000
URL:       https://git.openjdk.java.net/loom/commit/9fd4b017

Fix issue with not unregistering vthreads when they have exited. They were still appearing in the list of threads given to debuggers.

! src/jdk.jdwp.agent/share/native/libjdwp/threadControl.c