Allow concurrent CSV import

Issue Summary

Jira currently doesn't allow simultaneous CSV import following this procedure:

• Import data from a CSV file
   

Steps to Reproduce

1. Open the following screen in two different tabs or windows:
   • Go to Settings-> Import and Export-> External System Import-> CSV
2. Move forward with both import configurations until the last stage(Values)
3. Hit Begin Import button at the same time

Expected Results

Both imports to be completed independently

Actual Results

Only one import will complete. The other one will inherit the completion information from the last imported CSV.

Workaround

There is no workaround to import multiple CSVs simultaneously.