Add lock owner thread information to slow requests.

Also removed an unnecessary call to obtain a thread dump.
Using `ThreadInfo.toString` is probably a good idea, as it includes richer information than we were previously printing. However you want to print the elapsed time _before_ the stack trace, not after. And printing the thread name is redundant since `ThreadInfo.toString` includes that.

You should actually simulate some slow requests and see what the result looks like. My test case was something like this, in `/script`:

```
def t = Thread.currentThread();
def n = t.name;
for (int i = 0; ; i++) {
    t.name = "${n} at #${i}";
    Thread.sleep(1000);
}
```

but ideally you would do something that acquires locks, etc.