RFR(S):8251374:jmap -dump should not accept invalid options

[linzang(臧琳)]

Hi All, 
     May I ask your help to review this tiny patch? It fix an issue that jmap -dump could wrongly accept invalid optioins.
     Bugs: https://bugs.openjdk.java.net/browse/JDK-8251374
     Patch:  (Can not connect to webrev ftp currently, will try it later, following are all code changes)

################################
--- old/src/jdk.jcmd/share/classes/sun/tools/jmap/JMap.java	2020-08-11 10:42:32.044567791 +0800
+++ new/src/jdk.jcmd/share/classes/sun/tools/jmap/JMap.java	2020-08-11 10:42:31.876568681 +0800
@@ -207,6 +207,11 @@
                 liveopt = "-live";
             } else if (subopt.startsWith("file=")) {
                 filename = parseFileName(subopt);
+            } else if (subopt.equals("format=b")) {
+                // ignore format (not needed at this time)
+            } else {
+               System.err.println("Fail: invalid option: '" + subopt +"'");
+               System.exit(1);
             }
         }
################################

Thanks,
Lin