discoverNode(nodeID) {
		return this.publish(new Packet(P.PACKET_DISCOVER, nodeID)).catch(
			/* istanbul ignore next */ err => {
				this.logger.error(`Unable to send DISCOVER packet to '${nodeID}' node.`, err);

				this.broker.broadcastLocal("$transit.error", {
					error: err,
					module: "transit",
					type: C.FAILED_NODE_DISCOVERY
				});
			}
		);
	}
Discover a node. It will be called if we got message from an unknown node.

@memberof Transit