Fix new bulk import queuing

[rkorytkowski]

When scheduling some NPM packages the import does never end. The problematic package is hl7.fhir.r4.core:4.0.1. It enters an endless loop at the last group of tasks, which are being repeated in a loop.

[rkorytkowski]

The above fix is following https://stackoverflow.com/a/19018521, but it causes another issue of the initial task hanging (appears to be waiting for results) instead of returning quickly and executing all subtasks asynchronously. The subtasks do run, but extremely slow... In ECS the worker even fails healthchecks by not responding in time. Locally I just see missed heartbeats for workers. It'a very strange behavior.

[rkorytkowski]

Some smaller packages that I hand-crafted do import correctly... I'll attach them shortly.

[rkorytkowski]

hl7.fhir.r4.core-4.0.1-subset.zip
hl7.fhir.r4.core-4.0.1-subset-all-conceptmaps.zip