network: fix requestBlocks() for (headers == blocks + 1)

In the very specific case when the list of headers received is exactly one
block ahead of the chain of full blocks requestBlocks() failed to generate
request to get the next full block.

pkg/network/server.go

@@ -330,7 +330,7 @@ func (s *Server) requestBlocks(p Peer) error {
 		hashStart    = s.chain.BlockHeight() + 1
 		headerHeight = s.chain.HeaderHeight()
 	)
-	for hashStart < headerHeight && len(hashes) < maxBlockBatch {
+	for hashStart <= headerHeight && len(hashes) < maxBlockBatch {
 		hash := s.chain.GetHeaderHash(int(hashStart))
 		hashes = append(hashes, hash)
 		hashStart++