P2P find() optimization

[jmjatlanta]

Please see

bitshares-core/libraries/net/node.cpp

Lines 751 to 767 in 35ec65b

	for (const item_id& item_to_advertise : inventory_to_advertise)
	{
	if (peer->inventory_advertised_to_peer.find(item_to_advertise) != peer->inventory_advertised_to_peer.end() )
	idump((*peer->inventory_advertised_to_peer.find(item_to_advertise)));
	if (peer->inventory_peer_advertised_to_us.find(item_to_advertise) != peer->inventory_peer_advertised_to_us.end() )
	idump((*peer->inventory_peer_advertised_to_us.find(item_to_advertise)));
	if (peer->inventory_advertised_to_peer.find(item_to_advertise) == peer->inventory_advertised_to_peer.end() &&
	peer->inventory_peer_advertised_to_us.find(item_to_advertise) == peer->inventory_peer_advertised_to_us.end())
	{
	items_to_advertise_by_type[item_to_advertise.item_type].push_back(item_to_advertise.item_hash);
	peer->inventory_advertised_to_peer.insert(peer_connection::timestamped_item_id(item_to_advertise, fc::time_point::now()));
	++total_items_to_send_to_this_peer;
	if (item_to_advertise.item_type == trx_message_type)
	testnetlog("advertising transaction ${id} to peer ${endpoint}", ("id", item_to_advertise.item_hash)("endpoint", peer->get_remote_endpoint()));
	dlog("advertising item ${id} to peer ${endpoint}", ("id", item_to_advertise.item_hash)("endpoint", peer->get_remote_endpoint()));
	}

It appears that the find() on these 2 collections are being called 3 times each, while 1 should suffice.