Add logic to only download and store one package at a time

[helrond]

Is your feature request related to a problem? Please describe.

Trying to download or store multiple packages at once often causes tasks to time out because both of these services push binary data over HTTP. This has a host of unfortunate effects downstream and can be a huge headache to troubleshoot.

Describe the solution you'd like

Implement logic so that the download and store services only process one package at a time.