Default force attr to true on LinkButton

This retains beta 13 behavior.

js/src/common/components/LinkButton.js

@@ -12,12 +12,14 @@ import Link from './Link';
  *   active.
  * - `href` The URL to link to. If the current URL `m.route()` matches this,
  *   the `active` prop will automatically be set to true.
+ * - `force` Whether the page should be fully rerendered. Defaults to `true`.
  */
 export default class LinkButton extends Button {
   static initAttrs(attrs) {
     super.initAttrs(attrs);
 
     attrs.active = this.isActive(attrs);
+    if (attrs.force === undefined) attrs.force = true;
   }
 
   view(vnode) {