The Fuzzer can run killOp on the JournalFlusher thread and cause it to throw an unexpected error

The fuzzer appears to have run killOp against the journal flusher thread. At least, right after there's a log about killing op with opId 8221, the journal flusher gets interrupted with the same error message as OperationContext::checkForInterruptNoAssert, which can be called from the locking code (the journal flusher takes a lock to do a write to the oplogTruncateAfterPoint), can return.