./check_pool_local_putget may hang while demanding a CDO

./check_pool_local_putget sometimes hangs during what looks like waiting for a CDO.

[D] POOL t139851265947392 (ortolan 29045) 25333624456087: mstro_cdo_demand(cdo.c:736) Demanding CDO `Work item 19' (id 0d0ec085-5494-5807-9d67-ad84124b9f95) from pool

[D] POOL t139851265947392 (ortolan 29045) 25333624459910: mstro_pmp_send_nowait(pool_manager_protocol.c:91) handling msg mstro.pool.Demand to 1

[D] POOL t139851265947392 (ortolan 29045) 25333624462673: mstro_pmp_send_nowait(pool_manager_protocol.c:101) No pool manager, no need to send message of type mstro.pool.MstroMsg to app id 1

[D] POOL t139851265947392 (ortolan 29045) 25333624465411: mstro_pool__demand(pool.c:778) demand local only, no PM

[D] POOL t139851265947392 (ortolan 29045) 25333624468132: mstro_pool__demand(pool.c:834) No suitable provider; wait on pool entry 0x7f319c0188c0, CDO `Work item 19' (id 0d0ec085-5494-5807-9d67-ad84124b9f95), 1 total waiters

On my Ubuntu desktop machine this happens about half of the times. It looks like a threading issue.