journal-file: always generate the same error when encountering corrupted files

Let's make sure EBADMSG is the one error we throw when we encounter corrupted
data, so that we can neatly test for it.

src/journal/journal-file.c

@@ -707,7 +707,7 @@ int journal_file_move_to_object(JournalFile *f, ObjectType type, uint64_t offset
 
         /* Objects may only be located at multiple of 64 bit */
         if (!VALID64(offset))
-                return -EFAULT;
+                return -EBADMSG;
 
         /* Object may not be located in the file header */
         if (offset < le64toh(f->header->header_size))