Set SNI ClientHello extension to localhost in tests

The connection strings in the SSL client tests were using the host
set up from Cluster.pm which is a temporary pathname. When SNI is
enabled we pass the host to OpenSSL in order to set the server name
indication ClientHello extension via SSL_set_tlsext_host_name.

OpenSSL doesn't validate the hostname apart from checking the max
length, but LibreSSL checks for RFC 5890 conformance which results
in errors during testing as the pathname from Cluster.pm is not a
valid hostname.

Fix by setting the host explicitly to localhost, as that's closer
to the intent of the test.

Backpatch through 14 where SNI support came in.
Reported-by: Nazir Bilal Yavuz <byavuz81@gmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/17391-304f81bcf724b58b@postgresql.org
Backpatch-through: 14

src/test/ssl/t/001_ssltests.pl

@@ -388,7 +388,7 @@ $node->connect_fails(
 note "running server tests";
 
 $common_connstr =
-  "sslrootcert=ssl/root+server_ca.crt sslmode=require dbname=certdb hostaddr=$SERVERHOSTADDR";
+  "sslrootcert=ssl/root+server_ca.crt sslmode=require dbname=certdb hostaddr=$SERVERHOSTADDR host=localhost";
 
 # no client cert
 $node->connect_fails(
@@ -538,7 +538,7 @@ $node->connect_fails(
 # works, iff username matches Common Name
 # fails, iff username doesn't match Common Name.
 $common_connstr =
-  "sslrootcert=ssl/root+server_ca.crt sslmode=require dbname=verifydb hostaddr=$SERVERHOSTADDR";
+  "sslrootcert=ssl/root+server_ca.crt sslmode=require dbname=verifydb hostaddr=$SERVERHOSTADDR host=localhost";
 
 $node->connect_ok(
 	"$common_connstr user=ssltestuser sslcert=ssl/client.crt sslkey=ssl/client_tmp.key",
@@ -565,7 +565,7 @@ $node->connect_ok(
 # intermediate client_ca.crt is provided by client, and isn't in server's ssl_ca_file
 switch_server_cert($node, 'server-cn-only', 'root_ca');
 $common_connstr =
-  "user=ssltestuser dbname=certdb sslkey=ssl/client_tmp.key sslrootcert=ssl/root+server_ca.crt hostaddr=$SERVERHOSTADDR";
+  "user=ssltestuser dbname=certdb sslkey=ssl/client_tmp.key sslrootcert=ssl/root+server_ca.crt hostaddr=$SERVERHOSTADDR host=localhost";
 
 $node->connect_ok(
 	"$common_connstr sslmode=require sslcert=ssl/client+client_ca.crt",

src/test/ssl/t/002_scram.pl

@@ -53,7 +53,7 @@ configure_test_server_for_ssl($node, $SERVERHOSTADDR, $SERVERHOSTCIDR,
 switch_server_cert($node, 'server-cn-only');
 $ENV{PGPASSWORD} = "pass";
 $common_connstr =
-  "dbname=trustdb sslmode=require sslcert=invalid sslrootcert=invalid hostaddr=$SERVERHOSTADDR";
+  "dbname=trustdb sslmode=require sslcert=invalid sslrootcert=invalid hostaddr=$SERVERHOSTADDR host=localhost";
 
 # Default settings
 $node->connect_ok(
@@ -99,7 +99,7 @@ my $client_tmp_key = "ssl/client_scram_tmp.key";
 copy("ssl/client.key", $client_tmp_key);
 chmod 0600, $client_tmp_key;
 $node->connect_fails(
-	"sslcert=ssl/client.crt sslkey=$client_tmp_key sslrootcert=invalid hostaddr=$SERVERHOSTADDR dbname=certdb user=ssltestuser channel_binding=require",
+	"sslcert=ssl/client.crt sslkey=$client_tmp_key sslrootcert=invalid hostaddr=$SERVERHOSTADDR host=localhost dbname=certdb user=ssltestuser channel_binding=require",
 	"Cert authentication and channel_binding=require",
 	expected_stderr =>
 	  qr/channel binding required, but server authenticated client without channel binding/
@@ -107,7 +107,7 @@ $node->connect_fails(
 
 # Certificate verification at the connection level should still work fine.
 $node->connect_ok(
-	"sslcert=ssl/client.crt sslkey=$client_tmp_key sslrootcert=invalid hostaddr=$SERVERHOSTADDR dbname=verifydb user=ssltestuser",
+	"sslcert=ssl/client.crt sslkey=$client_tmp_key sslrootcert=invalid hostaddr=$SERVERHOSTADDR host=localhost dbname=verifydb user=ssltestuser",
 	"SCRAM with clientcert=verify-full",
 	log_like => [
 		qr/connection authenticated: identity="ssltestuser" method=scram-sha-256/