Fix ProfilePolicyConnector shutdown in TestingProfile.
Fix ProfilePolicyConnector shutdown in TestingProfile.

BrowserPolicyConnector was incorrectly created in ProfilePolicyConnector::Shutdown.
Thus, some unit tests that shouldn't have a dependency on BrowserPolicyConnector did implicitly create it nonetheless if they use TestingProfile.

Review URL: https://codereview.chromium.org/1304743004

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#344482}

ltilve/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend