private boolean isMemberShuttingDown(ID dm) {
    shutdownMembersReadLock.lock();
    try {
      return shutdownMembers.contains(dm);
    } finally {
      shutdownMembersReadLock.unlock();
    }
  }
Remove a member. {@link #latestViewWriteLock} must be held before this method is called. If
member is not already shunned, the uplevel event handler is invoked.
geode-membership/src/main/java/org/apache/geode/distributed/internal/membership/gms/GMSMembership.java