clone volume locations in case they are changed

fix https://github.com/seaweedfs/seaweedfs/issues/4642

weed/shell/command_ec_encode.go

@@ -98,7 +98,7 @@ func doEcEncode(commandEnv *CommandEnv, collection string, vid needle.VolumeId,
 	}
 
 	// find volume location
-	locations, found := commandEnv.MasterClient.GetLocations(uint32(vid))
+	locations, found := commandEnv.MasterClient.GetLocationsClone(uint32(vid))
 	if !found {
 		return fmt.Errorf("volume %d not found", vid)
 	}