Cloud statistics complains when deleting some nodes

I have no idea why this appears in logs sometimes:

```
WARNING: No activity tracked for ProvisioningActivity for ciosp/rhel7-medium/null (1492330605)
java.lang.IllegalStateException
at org.jenkinsci.plugins.cloudstats.CloudStatistics.getActivityFor(CloudStatistics.java:160)
at jenkins.plugins.openstack.compute.JCloudsSlave$RecordDisposal.dispose(JCloudsSlave.java:199)
at org.jenkinsci.plugins.resourcedisposer.AsyncResourceDisposer$WorkItem.run(AsyncResourceDisposer.java:286)
at jenkins.util.ContextResettingExecutorService$1.run(ContextResettingExecutorService.java:28)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:748)
```

The absence of activity name suggests it might have never got launched successfully. But the activity should have existed for that. An explanation for activity missing might be it was completed already, presumably because the disposer is struggling to get it removed repeatedly, and rotated consequently.

Though to myself: While we can workaround this by accepting the activity is gone already when the resource is still tracked by resource-disposer, the question is if we want to consider such activity completed on the first place. it is not operating either, though.