tasks are not always run in parallel when multiple pulp-workers are available

Description

If multiple collections are uploaded simultaneously or in quick succession, only a single pulp-worker processes the tasks even if multiple are available

This is seen in beta-galaxy-stage during performance tests, and in c.rh.c stage during integration tests.

Key Dependency Versions

{"available_versions":\{"v3":"v3/","pulp-v3":"pulp/api/v3/","v1":"v1/"}

,"server_version":"4.8.0dev","galaxy_ng_version":"4.8.0dev","galaxy_ng_commit":"master:3779fd07","galaxy_importer_version":"0.4.11","pulp_core_version":"3.28.7","pulp_ansible_version":"0.19.0","pulp_container_version":"2.15.1"}

Steps to Reproduce

upload multiple collections

Actual Behavior

check '/api/automation-hub/v3/tasks/?state=running' to see only 1 task is running

check '/api/automation-hub/v3/tasks/?state=waiting' to see the remaining upload tasks are waiting

Expected Behavior

each pulp-worker should be processing available waiting tasks