Tests: workaround for broken TLSv1.3 sigalgs in LibreSSL.

Although RSA certificate selection is currently [1] broken to complete
handshake, it happens late after sending all server handshake messages.
This is enough for tests to pick up the corresponding certificate type.
Workaround is to avoid sending application data resulting in SIGPIPE.

[1] openbsd/src@ccf5fc6

Author: pluknet

ssl_certificates.t

@@ -43,8 +43,6 @@ http {
     ssl_certificate rsa.crt;
     ssl_ciphers DEFAULT:ECCdraft;
 
-    add_header X-SSL-Protocol $ssl_protocol;
-
     server {
         listen       127.0.0.1:8443 ssl;
         server_name  localhost;
@@ -85,28 +83,15 @@ foreach my $name ('ec', 'rsa') {
 		or die "Can't create certificate for $name: $!\n";
 }
 
-$t->write_file('index.html', '');
-
 $t->run()->plan(2);
 
 ###############################################################################
 
-TODO: {
-local $TODO = 'broken TLSv1.3 sigalgs in LibreSSL'
-	if $t->has_module('LibreSSL') && test_tls13();
-
 like(cert('RSA'), qr/CN=rsa/, 'ssl cert RSA');
-
-}
-
 like(cert('ECDSA'), qr/CN=ec/, 'ssl cert ECDSA');
 
 ###############################################################################
 
-sub test_tls13 {
-	return http_get('/', SSL => 1) =~ /TLSv1.3/;
-}
-
 sub cert {
 	my $s = get_socket(@_) || return;
 	return $s->dump_peer_certificate();
@@ -128,8 +113,8 @@ sub get_socket {
 			or die("Failed to set sigalgs");
 	};
 
-	return http_get(
-		'/', start => 1,
+	return http(
+		'', start => 1,
 		SSL => 1,
 		SSL_cipher_list => $type,
 		SSL_create_ctx_callback => $ctx_cb