@Override
  void close() {
    dm.removeMembershipListener(this);
  }
Checks to make sure that the number of application members of the distributed system that have
left unexpected since the last evaluation is less than the
{@linkplain DistributedSystemHealthConfig#getMaxDepartedApplications threshold}. If not, the
status is "poor" health.
geode-core/src/main/java/org/apache/geode/admin/internal/DistributedSystemHealthEvaluator.java