fix replication range check

fix for https://github.com/seaweedfs/seaweedfs/wiki/Replication#replication-string

weed/storage/super_block/replica_placement.go

@@ -1,7 +1,6 @@
 package super_block
 
 import (
-	"errors"
 	"fmt"
 )
 
@@ -15,18 +14,21 @@ func NewReplicaPlacementFromString(t string) (*ReplicaPlacement, error) {
 	rp := &ReplicaPlacement{}
 	for i, c := range t {
 		count := int(c - '0')
-		if 0 <= count && count <= 2 {
-			switch i {
-			case 0:
-				rp.DiffDataCenterCount = count
-			case 1:
-				rp.DiffRackCount = count
-			case 2:
-				rp.SameRackCount = count
-			}
-		} else {
-			return rp, errors.New("Unknown Replication Type:" + t)
+		if count < 0 {
+			return rp, fmt.Errorf("unknown replication type: %s", t)
 		}
+		switch i {
+		case 0:
+			rp.DiffDataCenterCount = count
+		case 1:
+			rp.DiffRackCount = count
+		case 2:
+			rp.SameRackCount = count
+		}
+	}
+	value := rp.DiffDataCenterCount*100 + rp.DiffRackCount*10 + rp.SameRackCount
+	if value > 255 {
+		return rp, fmt.Errorf("unexpected replication type: %s", t)
 	}
 	return rp, nil
 }