cherry-pick from 10.10

MDEV-29608 Default SSL makes mysqlslap much slower, tests fail with timeout

mysqlslap has an unusual semantics of the --iterations option, so that
$ mysqlslap --concurrency=16 --iterations=1000
performs 16,000 connections. Because of that it gets many times slower
with --ssl

Let's disable ssl for mysqlslap in mysql-test

mysql-test/include/default_client.cnf

@@ -18,6 +18,9 @@ default-character-set=latin1
 [mysql_upgrade]
 default-character-set=latin1
 
+[mysqlslap]
+loose-skip-ssl
+
 [mysqltest]
 loose-ssl-ca=@ENV.MYSQL_TEST_DIR/std_data/cacert.pem
 loose-ssl-cert=@ENV.MYSQL_TEST_DIR/std_data/client-cert.pem