network: try connecting to seeds indefinitely, use them with 0 pool

If the node is to start with seeds unavailable it will try connecting to each
of them three times, blacklist them and then sit forever waiting for
something. It's not a good behavior, it should always try connecting to seeds
if nothing else works.

pkg/network/server.go

@@ -151,6 +151,7 @@ func NewServer(config ServerConfig, chain blockchainer.Blockchainer, log *zap.Lo
 
 	s.transport = NewTCPTransport(s, net.JoinHostPort(config.Address, strconv.Itoa(int(config.Port))), s.log)
 	s.discovery = NewDefaultDiscovery(
+		s.Seeds,
 		s.DialTimeout,
 		s.transport,
 	)
@@ -171,8 +172,6 @@ func (s *Server) Start(errChan chan error) {
 
 	s.tryStartConsensus()
 
-	s.discovery.BackFill(s.Seeds...)
-
 	go s.broadcastTxLoop()
 	go s.relayBlocksLoop()
 	go s.bQueue.run()