void removeAndCloseThreadOwnedSockets() {
    Map<DistributedMember, Connection> m = threadOrderedConnMap.get();
    if (m != null) {
      // No need to synchronize map since it is only referenced by ThreadLocal.
      for (final Iterator<Map.Entry<DistributedMember, Connection>> it =
          m.entrySet().iterator(); it.hasNext();) {
        final Map.Entry<DistributedMember, Connection> me = it.next();
        DistributedMember stub = me.getKey();
        Connection c = me.getValue();
        removeFromThreadConMap(threadConnectionMap, stub, c);
        it.remove();
        closeCon("thread finalization", c);
      }
    }
  }
Clears lastInstance. Does not yet close underlying sockets, but probably not strictly
necessary.

@see SystemFailure#emergencyClose()
geode-core/src/main/java/org/apache/geode/internal/tcp/ConnectionTable.java