VM hangs in shutdown under this scenario (thread 1 is main thread, thread 2
could be any daemon thread but in this test it is the JVMPI sampler thread):

1. Thread 2 tries to suspend thread 1, it marks _external_suspend for thread 1
   and queues up a VM_ThreadSuspend operation.
2. At the same time, thread 1 is in destroy_vm. It calls thread->exit().
3. VM_ThreadSuspend and then java_resume() are executed on thread 1. But they
   have no effect since thread 1 is "terminated".
4. Thread 1 continues to execute in VMThread::execute(VM_SuspendDaemons). It
   needs to lock VMOperationRequest_lock. Because thread 1 is Java thread,
   this will eventually call Mutex::wait_for_lock_blocking_implementation.
5. _external_suspend remains true, so thread 1 will loop forever in
   wait_for_lock_blocking_implementation (java_suspend_self does nothing
   because thread 1 is "terminated").