MXS-3259: Add default connection timeout

The connector never times out if one is not defined. This seems to help
make the mxs1985_kill_hang test a lot more stable.

system-test/maxtest/src/mariadb_func.cc

@@ -50,6 +50,9 @@ MYSQL* open_conn_db_flags(int port,
         set_ssl(conn);
     }
 
+    unsigned int timeout = 15;
+    mysql_options(conn, MYSQL_OPT_CONNECT_TIMEOUT, &timeout);
+
     // MXS-2568: This fixes mxs1828_double_local_infile
     mysql_optionsv(conn, MYSQL_OPT_LOCAL_INFILE, (void*)"1");