Churn governor: give head start for local root peers

See the comment [here](https://github.com/input-output-hk/ouroboros-network/blob/master/ouroboros-network/src/Ouroboros/Network/PeerSelection/Governor.hs?plain=1#L603-L605):
```hs
-- TODO: revisit the policy once we have local root peers in the governor.
-- The intention is to give local root peers give head start and avoid
-- giving advantage to hostile and quick root peers.
threadDelay 3
```