BUG/MAJOR: http: null-terminate the http actions keywords list

Commit a0dc23f ("MEDIUM: http: implement http-request set-{method,path,query,uri}")
forgot to null-terminate the list, resulting in crashes when these actions
are used if the platform doesn't pad the struct with nulls.

Thanks to Gunay Arslan for reporting a detailed trace showing the
origin of this bug.

No backport to 1.5 is needed.

src/proto_http.c

@@ -12033,6 +12033,7 @@ struct http_req_action_kw_list http_req_actions = {
 		{ "set-path",   parse_set_req_line },
 		{ "set-query",  parse_set_req_line },
 		{ "set-uri",    parse_set_req_line },
+		{ NULL, NULL }
 	}
 };