System restore functionality skips ActiveObjects data import if a single XML file is specified

Issue Summary

One can specify a single XML file containing entities data when using the Restore system funcionality. When this is done, Jira will only import entities and skip importing ActiveObjects entirely.

Steps to Reproduce

1. Generate an XML backup by navigating to Cog Icon > System > Backup system.
2. Place the generated zip file inside JIRA_HOME/import and unzip it in order to expose the files entities.xml and activeobjects.xml.
3. Navigate to Cog Icon > System > Restore system and fill in the value entities.xml for the field File name.
4. Click Restore.

Expected Results

Jira should only accept a zip file containing both entities.xml and activeobjects.xml, aborting the process if a different file type is specified.

Actual Results

Jira will only import the entities in the provided file, and nothing else. ActiveObjects import will be completely skipped.

This will cause all information stored in AO tables to not be imported. Such data includes:

• Agile boards.
• Sprints.
• Issue ranking data.
• Webhooks.
• Most data used by Atlassian's or third-party apps.

No errors or exceptions regarding partial data being imported are logged.

Workaround

Make sure to specify a zip file containing both entities.xml and activeobjects.xml.