config: adds an extra tls ip to config

This commit adds the `tlsextraip` flag to the cli to add an
ip to the generated certificate. This is usefull when using
a loadbalancer to access the node.

lnd.go

@@ -608,6 +608,12 @@ func genCertPair(certFile, keyFile string) error {
 		}
 	}
 
+	// Add extra IP to the slice.
+	ipAddr := net.ParseIP(cfg.TLSExtraIP)
+	if ipAddr != nil {
+		addIP(ipAddr)
+	}
+
 	// Collect the host's names into a slice.
 	host, err := os.Hostname()
 	if err != nil {