Run peer refresh and discovery

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Currently peer are only added, when received.
it is ok as long as we periodically publish peer, this is another issue and should be manage by application or see propagate keycache [https://github.com//issues/35].
This is ok but when route reply with not enough result we need new now so
TODO

• add peer discovery and connection refresh on get_closest_peer with not enough result -> route need new interface
  • one to send disconnect peer which should be refresh (get_closest should return a pair with connected vec and (non connected vec * factor) to complete in not enough peer) -> the mult factor should be in a rule and added to get_closest (at start it should be omit).
  • one to tell if peer discovery is needed (and the number needed) : otherwhise as long as we send to n peer we could have an route with only n peer which for some network could be insecure. This should be called periodically (param by rule), by peermanagement process (see querycache cleaning).

[cheme]

Connection is retry once in client before failure.
Peer refresh is possible with peermanager (see new route interface to get multiple peer then just ping).