we must only return io.EOF to progress to the next file in auto.Group

since we never write msg partially, if we've encountered io.EOF in the
middle of the msg, we must abort

consensus/wal.go

@@ -273,9 +273,6 @@ func (dec *WALDecoder) Decode() (*TimedWALMessage, error) {
 
 	b = make([]byte, 4)
 	_, err = dec.rd.Read(b)
-	if err == io.EOF {
-		return nil, err
-	}
 	if err != nil {
 		return nil, fmt.Errorf("failed to read length: %v", err)
 	}
@@ -287,9 +284,6 @@ func (dec *WALDecoder) Decode() (*TimedWALMessage, error) {
 
 	data := make([]byte, length)
 	_, err = dec.rd.Read(data)
-	if err == io.EOF {
-		return nil, err
-	}
 	if err != nil {
 		return nil, fmt.Errorf("failed to read data: %v", err)
 	}