Automatic reindexing can trigger unnecessarily

Steps to reproduce:

1. Set up a one node cluster
2. Either populate the instance with a lot of data or disable index flushing job so that reindexing will block index flush from happening during startup
3. Stop the node
4. Remove ${CONFLUENCE_HOME}/journal/main_index file
5. Start the node and let reindexing complete
6. Restart the node

Outcome: Reindexing is triggered again

Suggested fix: Update journal id to be the id of the latest entry in journalentry table at the beginning of reindexing.