Originally reported at:

https://github.com/ovn-org/ovn-kubernetes/issues/4301

The lexer_parse_template_string() function is used to parse all templates in a LB VIP/backend or lflow.  However, if templates can't be instantiated on a given chassis (e.g., missing Chassis_Template_Var value) it's left untouched, e.g., (^NODEIP_IPv4_2) and further parsing is still attempted:

if (lexer.token.type == LEX_T_TEMPLATE) {
            ds_put_cstr(&expanded, smap_get_def(template_vars, lexer.token.s,                                                lexer.token.s));  <<< failure to expand leaves the token as is
            if (template_vars_ref) {
                sset_add(template_vars_ref, lexer.token.s);
            } 

This generates warnings when trying to parse the lflow or the IP address.

Ideally, lexer_parse_template_string() should return a value to indicate whether templates have been successfully expanded.  The LBs/lflows that contain templates that cannot be expanded not should be further parsed.