[CrOS MultiDevice] DeviceReenroller: Don't store local device metadata as ref

The helper function
DeviceReenroller::GetSupportedFeaturesForLocalDevice() is currently
storing a local variable as a const ref. This is breaking
chromeos_unittests when the following `gn args` are used:

    ffmpeg_branding = "ChromeOS"
    is_component_build = false
    is_debug = false
    proprietary_codecs = true
    strip_absolute_paths_from_debug_symbols = true
    target_os = "chromeos"
    use_goma = true
    use_vaapi = true

Bug: 887557
Change-Id: Iaa805f645b5cefc2ab93ca46e595886e5e00e6dc
Tested: chromeos_unittests with gn args listed above
Reviewed-on: https://chromium-review.googlesource.com/1236512
Commit-Queue: Josh Nohle <nohle@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#592891}

chromeos/services/multidevice_setup/device_reenroller.cc

@@ -139,7 +139,7 @@ void DeviceReenroller::AttemptReenrollmentIfNecessary() {
 
 std::vector<cryptauth::SoftwareFeature>
 DeviceReenroller::GetSupportedFeaturesForLocalDevice() {
-  const cryptauth::RemoteDeviceRef& local_device_metadata =
+  const cryptauth::RemoteDeviceRef local_device_metadata =
       *device_sync_client_->GetLocalDeviceMetadata();
 
   base::flat_set<cryptauth::SoftwareFeature> sorted_and_deduped_set;