policy: don't link endpoints on startup
Sometimes the default device node might not exist when reevaluating endpoints for the first time on startup, so the policy would link endpoints to another device node. Then, the default device node appears and the policy moves the endpoints to the default device node while the previous link has not finish its activation yet. This race condition can cause endpoint links to fail when being activated. Delaying the reevaluation of endpoint links until the first client link is created avoids this issue.