skip network error when remote volumes start

weed/storage/super_block/replica_placement.go

@@ -36,6 +36,9 @@ func NewReplicaPlacementFromByte(b byte) (*ReplicaPlacement, error) {
 }
 
 func (rp *ReplicaPlacement) Byte() byte {
+	if rp == nil {
+		return 0
+	}
 	ret := rp.DiffDataCenterCount*100 + rp.DiffRackCount*10 + rp.SameRackCount
 	return byte(ret)
 }

weed/storage/volume_loading.go

@@ -84,6 +84,11 @@ func (v *Volume) load(alsoLoadIndex bool, createDatIfMissing bool, needleMapKind
 	if alreadyHasSuperBlock {
 		err = v.readSuperBlock()
 		glog.V(0).Infof("readSuperBlock volume %d version %v", v.Id, v.SuperBlock.Version)
+		if v.HasRemoteFile() {
+			// maybe temporary network problem
+			glog.Errorf("readSuperBlock remote volume %d: %v", v.Id, err)
+			err = nil
+		}
 	} else {
 		if !v.SuperBlock.Initialized() {
 			return fmt.Errorf("volume %s not initialized", v.FileName(".dat"))