Every start up of Jira 8 shows "Purging JIRA_HOME\caches\indexes - index file not compatible with Lucene 7.x" in the logs.

Issue Summary

Every time Jira 8.2.2 is started up, there would be a line in the logs that show:

2019-07-09 17:54:12,569 JIRA-Bootstrap INFO      [c.a.jira.index.ObsoleteIndexCleaner] Purging F:\Program Files\Atlassian\Application Data\JIRAGHS-155969\caches\indexes - index file not compatible with Lucene 7.x

Environment

Jira 8.2.2 that was updated from Jira 7.9.2. (needs to be validated)

Steps to Reproduce

1. Install Jira 7.9.2.
2. Populate Jira 7.9.2 with some issues, and run a re-index.
3. Update Jira 7.9.2 -> Jira 8.2.2
4. Startup Jira 8.2.2.
5. The following lines would be observed:

   2019-07-09 17:45:00,453 JIRA-Bootstrap INFO      [c.a.jira.index.ObsoleteIndexCleaner] Purging F:\Program Files\Atlassian\Application Data\JIRAGHS-155969\caches\indexes - index file not compatible with Lucene 7.x
   

6. Restart Jira 8.2.2.
7. Again, the logs would show:

   2019-07-09 17:48:40,685 JIRA-Bootstrap INFO      [c.a.jira.index.ObsoleteIndexCleaner] Purging F:\Program Files\Atlassian\Application Data\JIRAGHS-155969\caches\indexes - index file not compatible with Lucene 7.x
   

Expected Results

It should only show that the old indexes are purged once.

Actual Results

Every startup, would show a line that says the indexes are purged.

Workaround

Jira tries to delete old Index folder during each start. It's safe to ignore the logging message.