Set value before activating another extruder

Because all extruder tabs share the same SettingPropertyProvider, we want the property provider value to update before its container stack is changed, or the value carries over to the other containerstack, leaving the value for the initial containerstack unchanged

plugins/MachineSettingsAction/MachineSettingsAction.qml

@@ -476,6 +476,7 @@ Cura.MachineAction
             {
                 if(currentIndex > 0)
                 {
+                    contentItem.forceActiveFocus();
                     ExtruderManager.setActiveExtruderIndex(currentIndex - 1);
                 }
             }