6714244: Plotters in MBeans tab should use SnapshotMBeanServerConnection too

Reviewed-by: jfdenise

src/share/classes/sun/tools/jconsole/inspector/XPlottingViewer.java

@@ -157,7 +157,7 @@ public class XPlottingViewer extends PlotterPanel implements ActionListener {
                             public void run() {
                                 try {
                                     Number n =
-                                        (Number) xmbean.getMBeanServerConnection().getAttribute(xmbean.getObjectName(), attributeName);
+                                        (Number) xmbean.getSnapshotMBeanServerConnection().getAttribute(xmbean.getObjectName(), attributeName);
                                     long v;
                                     if (n instanceof Float || n instanceof Double) {
                                         plotter.setDecimals(PLOTTER_DECIMALS);