rpl.rpl_domain_id_filter_master_crash failed on msan builder

it seems that the test can get IO thread running or not,
there's a comment about it. Thus stop_slave_io.inc is told
to ignore errors.

Make stop_slave_io.inc also disable warnings in this case,
in particular "1255 Slave already has been stopped"

mysql-test/include/stop_slave_io.inc

@@ -34,8 +34,17 @@ if (!$rpl_debug)
   --disable_query_log
 }
 
-
+let $_enable_warnings=0;
+if ($rpl_allow_error) {
+  if ($ENABLED_WARNINGS) {
+    let $_enable_warnings=1;
+    disable_warnings;
+  }
+}
 STOP SLAVE IO_THREAD;
+if ($_enable_warnings) {
+  enable_warnings;
+}
 --source include/wait_for_slave_io_to_stop.inc