Memory leak detected in test_hierarchy_device

`test_hierarchy_device` is reporting
```
!!! detected some memory leaks in the code: trying to free non-empty temporary device pool !!!
34: ptr:     0x7f21e8006000 size: 3117056
34: ptr:     0x7f21e82ff000 size: 32768
34: ptr:     0x7f21e8307000 size: 32768
34: ptr:     0x7f21e830f000 size: 1560576
34: ptr:     0x7f21e848c000 size: 36864
34: ptr:     0x7f21e8495000 size: 36864
```