[PATCH] upas/smtpd: use the full chain of certificates with TLS

Otherwise, the other side won't be able to verify our certfificate.
Google will report this with the smtp-tls report.
---
diff 2cbda95fa2b7f49e11e86087b9718fde32cb11ad 9d0275079df5d31ba6c0e26f9bc1aaf5710a3501
--- a/sys/src/cmd/upas/smtp/smtpd.c
+++ b/sys/src/cmd/upas/smtp/smtpd.c
@@ -1585,8 +1585,7 @@
 void
 starttls(void)
 {
-	int certlen, fd;
-	uchar *cert;
+	int fd;
 	TLSconn conn;
 
 	if (tlscert == nil) {
@@ -1593,15 +1592,16 @@
 		reply("500 5.5.1 illegal command or bad syntax\r\n");
 		return;
 	}
-	cert = readcert(tlscert, &certlen);
-	if (cert == nil) {
+	memset(&conn, 0, sizeof(conn));
+	conn.chain = readcertchain(tlscert);
+	if (conn.chain == nil) {
 		reply("454 4.7.5 TLS not available\r\n");
 		return;
 	}
 	reply("220 2.0.0 Go ahead make my day\r\n");
-	memset(&conn, 0, sizeof(conn));
-	conn.cert = cert;
-	conn.certlen = certlen;
+	conn.cert = conn.chain->pem;
+	conn.certlen = conn.chain->pemlen;
+	conn.chain = conn.chain->next;
 	fd = tlsServer(Bfildes(&bin), &conn);
 	if (fd < 0) {
 		syslog(0, "smtpd", "TLS start-up failed with %s", him);