fixed a bug in a test

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@11968 71c3de6d-444a-0410-be80-ed276b4c234a

test/src/test/java/hudson/scm/ScmTest.java

@@ -24,6 +24,10 @@ public class ScmTest extends HudsonTestCase {
                 callback[0] = true;
                 return true;
             }
+
+            private Object writeReplace() { // don't really care about save
+                return new NullSCM();
+            }
         });
         p.scheduleBuild2(0).get();
         p.delete();