While looking at JDK-8341310 I've discovered that the `EventGeneratorLoop` running container always runs for a fixed time: `30` seconds. That's irrespective of the attacher containers being done. Therefore, two iterations of the loop spawning this container running the fixed set of time will at least run `60` seconds. In my test runs using `-summary:time` it was `70` seconds:

```
Passed: containers/docker/TestJcmdWithSideCar.java
  build: 2.08 seconds
  compile: 2.068 seconds
  build: 4.842 seconds
  compile: 4.841 seconds
  driver: 70.776 seconds
Test results: passed: 1
```

I don't think this is needed. There ought to be a better way to handle this and kill the running container that we've attached to and are done with it. An attempt of this has been done during review of JDK-8341310, but it caused more problems so was left for a separate issue.