We can lose logs in the following situation:
Setup: Master A is primary, Master B is secondary. Current log is 0x4-0xfffffff.
1. Loss of network connectivity triggers Master A to lose primacy. Master A begins shutting down its journal.
2. Master B becomes primary
3. Master B writes a journal entry, causing the log to be rotated. This renames 0x4-0xfffffff to 0x4-0x9
4. Master A finishes shutting down and tries to complete the current log. It sees that 0x4-0x9 already exists, so it deletes it with the idea of renaming 0x4-0xfffffff to 0x4-0x9. However, after deleting 0x4-0x9 it realizes that 0x4-0xfffffff is gone, and the 0x4-0x9 log has been lost.
To fix this issue, we should skip trying to complete the current log during shutdown.