MDEV-25591 : Test case cleanups

galera_var_wsrep_on_off : Add wait conditions to make sure DDL is
replicated before continuing.

wsrep.[variables|variables_debug] :  Remove unnecessary parts
and add check to correct number of variables or skip

galera_ssl_reload: Add version check and SSL checks.

mysql-test/include/galera_variables_ok_debug.inc

@@ -0,0 +1,9 @@
+--disable_query_log
+
+--let $galera_variables_ok = `SELECT COUNT(*) = 50 FROM INFORMATION_SCHEMA.GLOBAL_VARIABLES WHERE VARIABLE_NAME LIKE 'wsrep%'`
+
+--if (!$galera_variables_ok) {
+	--skip Galera number of variables has changed!
+}
+
+--enable_query_log