CI test timeout in lusearch

[qinsoon]

I have noticed a few timeouts for JikesRVM in a few mmtk-core PRs, such as mmtk/mmtk-core#404 and mmtk/mmtk-core#382. Possibly we have a regression somewhere. Generally the tests should take ~40mins (including extreme_assertion tests), but sometimes it timed out in 90mins.

Timeout: https://github.com/mmtk/mmtk-core/runs/3259252789?check_suite_focus=true