Disposed of thread pools after using

'waiting' 10 threads (=5 threads x 2 pools) are increased per execution.

At first, threr are 10 threads:
```
pool-1-thread-1 (waiting)
    ....
pool-1-thread-5 (waiting)
pool-2-thread-1 (waiting)
    ....
pool-2-thread-5 (waiting)
```

After 1st test-app, threr are 20 threads:
```
pool-1-thread-1 (waiting)
    ....
pool-1-thread-5 (waiting)
pool-2-thread-1 (waiting)
    ....
pool-2-thread-5 (waiting)
pool-5-thread-1 (waiting)
    ....
pool-5-thread-5 (waiting)
pool-6-thread-1 (waiting)
    ....
pool-6-thread-5 (waiting)
```

After 2nd test-app, threr are 30 threads:
```
pool-1-thread-1 (waiting)
    ....
pool-1-thread-5 (waiting)
pool-2-thread-1 (waiting)
    ....
pool-2-thread-5 (waiting)
pool-5-thread-1 (waiting)
    ....
pool-5-thread-5 (waiting)
pool-6-thread-1 (waiting)
    ....
pool-6-thread-5 (waiting)
pool-9-thread-1 (waiting)
    ....
pool-9-thread-5 (waiting)
pool-10-thread-1 (waiting)
    ....
pool-10-thread-5 (waiting)
```