Reduce flakiness of tests relying on proceeding upon network connection

Fixed: 1069098
Fixed: 1068868
Change-Id: Ie16fdd37bd551ba637856034dea681741e371d9d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2148736Reviewed-by: Roman Sorokin [CET] <rsorokin@chromium.org>
Commit-Queue: Denis Kuznetsov [CET] <antrim@chromium.org>
Cr-Commit-Position: refs/heads/master@{#758830}

chrome/browser/resources/chromeos/login/oobe_network.js

@@ -113,8 +113,8 @@ Polymer({
    * @private
    */
   onShown_() {
+    this.$.networkSelectLogin.refresh();
     this.async(function() {
-      this.$.networkSelectLogin.refresh();
       if (this.isConnected_)
         this.$.nextButton.focus();
       else