Use MountGuestAndGetHash() instead of MountGuest() for retail mode

chrome/browser/chromeos/login/auth/parallel_authenticator.cc

Index: chrome/browser/chromeos/login/auth/parallel_authenticator.cc
diff --git a/chrome/browser/chromeos/login/auth/parallel_authenticator.cc b/chrome/browser/chromeos/login/auth/parallel_authenticator.cc
index fd3ed692ddd8444d96749ccb3ad11bfd37ced55d..2bfcecf36c40133b69a00c69fc6385f988904c23 100644
--- a/chrome/browser/chromeos/login/auth/parallel_authenticator.cc
+++ b/chrome/browser/chromeos/login/auth/parallel_authenticator.cc
@@ -329,8 +329,8 @@ void ParallelAuthenticator::LoginRetailMode() {
                            false));  // user_is_new
   remove_user_data_on_failure_ = false;
   ephemeral_mount_attempted_ = true;
-  MountGuest(current_state_.get(),
-             scoped_refptr<ParallelAuthenticator>(this));
+  MountGuestAndGetHash(current_state_.get(),
+                       scoped_refptr<ParallelAuthenticator>(this));
 }
 
 void ParallelAuthenticator::LoginOffTheRecord() {