fixes bug in soda where hdunum was confused with extnum

data-access/servlet/src/main/java/cutout/SodaImpl.java

@@ -78,7 +78,7 @@ class SodaImpl implements Soda
 		cmd[0] = "/usr/local/bin/vlkb";
 		cmd[1] = "cutout";
 		cmd[2] = fitsPaths.surveys() + "/" + relPathname;
-		cmd[3] = String.valueOf(hdunum);
+		cmd[3] = String.valueOf(hdunum - 1); // extnum = hdunum - 1
 		cmd[4] = coordString;
 		LOGGER.finest(String.join(" ", cmd));