journal: Don't try to write garbage if journal entry is corrupted
    
    If journal_file_data_payload() returns -EBADMSG or -EADDRNOTAVAIL,
    we skip the entry and go to the next entry, but we never modify
    the number of items that we pass to journal_file_append_entry_internal()
    if that happens, which means we could try to append garbage to the
    journal file.
    
    Let's keep track of the number of fields we've appended to avoid this
    problem.