cros: Disable online sign-in flow for user-adding screen

A lot of edge cases could happen during online signin. So disabling it
for the multiprofile user adding flow.

Fixed: 690187
Change-Id: Idce44f3ef3c63a9dbd9d9e32af07733cd317f836
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2202805
Commit-Queue: Roman Sorokin [CET] <rsorokin@chromium.org>
Reviewed-by: Thomas Tellier <tellier@google.com>
Cr-Commit-Position: refs/heads/master@{#769624}

ui/login/account_picker/chromeos_user_pod_row.js

@@ -1635,9 +1635,8 @@ cr.define('login', function() {
       if (this.user.legacySupervisedUser && !this.user.isDesktopUser) {
         this.showSupervisedUserSigninWarning();
       } else {
-        // Special case for multi-profiles sign in. We show users even if they
-        // are not allowed per policy. Restrict those users from starting GAIA.
-        if (this.multiProfilesPolicyApplied)
+        // Disable online sign-in flow for user-adding screen.
+        if (Oobe.getInstance().displayType == DISPLAY_TYPE.USER_ADDING)
           return;
 
         this.parentNode.showSigninUI(this.user.emailAddress);