8186503: sun/security/tools/jarsigner/DefaultSigalg.java failed after backport to JDK 6/7/8

Reviewed-by: bgopularam

src/share/classes/sun/security/tools/keytool/Main.java

@@ -1714,7 +1714,8 @@ public final class Main {
                 // hardcode for now as DEF_RSA_KEY_SIZE is still 1024
                 keysize = 2048; // SecurityProviderConstants.DEF_RSA_KEY_SIZE;
             } else if ("DSA".equalsIgnoreCase(keyAlgName)) {
-                keysize = SecurityProviderConstants.DEF_DSA_KEY_SIZE;
+                // hardcode for now as DEF_DSA_KEY_SIZE is still 1024
+                keysize = 2048;
             }
         }