Remove false debug assertion

If MaxScale is started without the appropriate permissions to the paths
pointed by default values, the debug assertion fails even though the
parameter is valid but not usable.

server/core/config.c

@@ -2512,9 +2512,6 @@ void config_add_defaults(CONFIG_CONTEXT *ctx, const MXS_MODULE_PARAM *params)
             if (params[i].default_value &&
                 config_get_param(ctx->parameters, params[i].name) == NULL)
             {
-                ss_dassert(config_param_is_valid(params, params[i].name,
-                                                 params[i].default_value, ctx));
-
                 bool rv = config_add_param(ctx, params[i].name, params[i].default_value);
                 MXS_ABORT_IF_FALSE(rv);
             }