Issue Summary

This is reproducible on Data Center: yes

When running Jira Cloud Migration Assistant on a Jira Data Center cluster of more than one node app, migration's onStartAppMigration() is called more than once sequentially.

It may be called once for each node in the cluster.

Apps should handle duplicate calls to their webhooks for these events, however this is still a bug as we should only be doing app migration for each app once per server to cloud migration.

Note that you may receive duplicate uploads with different S3 keys as each file is uploaded once for each node.

Steps to Reproduce

1. Run JCMA in Jira Data Center with more than one node
2. Run app migration for an app that implements an app migration listener

Expected Results

The events listener-triggered, and if used app-data-uploaded, are only sent once per call to onStartAppMigration() or createData()

Actual Results

The events listener-triggered, and if used app-data-uploaded, are sent once per  node per call to onStartAppMigration() or createData()

Workaround

Run Jira Data Center with only one node.