8251374: jmap -dump could accept invalid options

Emit usage(1) in dump() argument loop

Reviewed-by: sspitsyn, phh

src/jdk.jcmd/share/classes/sun/tools/jmap/JMap.java

@@ -216,6 +216,11 @@ public class JMap {
                 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 + "'");
+                usage(1);
             }
         }