Don't start Geoclue satellite providers until necessary.

This builds on 2509cc2f13b15de099c3d68769e9bce869400ef7. It implements
similar changes to the Geoclue satellite info source.

Change-Id: I657f110e049c84b35f534a3bfffd14d57ee9c37a
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>