Fix UserCloudPolicyTokenForwardTest failure caught by asan

Asan bots caught a unit test failure after 00722f1e
which is fixed by making sure the ProfileManager outlasts
the UserCloudPolicyManagerChromeOS

Bug: none
Change-Id: I5d3aef4dcc7e423bfdf1742469c8789b4edfd0d1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1872573Reviewed-by: Denis Kuznetsov <antrim@chromium.org>
Commit-Queue: Evan Stade <estade@chromium.org>
Cr-Commit-Position: refs/heads/master@{#708322}

chrome/browser/chromeos/policy/user_cloud_policy_token_forwarder_unittest.cc

@@ -115,6 +115,8 @@ class UserCloudPolicyTokenForwarderTest : public testing::Test {
 
   void TearDown() override {
     user_policy_manager_->core()->Disconnect();
+    // Must be torn down before |profile_manager_|.
+    user_policy_manager_.reset();
     chromeos::DBusThreadManager::Shutdown();
   }