Unlock repository during collection import

[newswangerd]

Is your feature request related to a problem? Please describe.
Right now collection imports lock the entire repository that the collection is being imported into (

pulp_ansible/pulp_ansible/app/galaxy/v3/views.py

Line 514 in 1528769

temp_file.pk, distro.repository, **kwargs

). This makes it so that only one collection can be imported at a time. This is problematic because the import task can take a long time, and doesn't need to maintain a lock on the repository for the full duration of the import.

Describe the solution you'd like
Remove the repository lock during collection import and have the collection import launch a subtask (with the repository lock) to move the collection into the selected repository after the import is successful.

Additional context
This is needed for repository management in galaxy_ng to get rid of inbound repositories.