Clear the pointer to destroyed object early using the semantic patch

Also disable the semantic patch as the code needs tweaks here and there because
some destroy functions might not destroy the object and return early if the
object is still in use.

bin/nsupdate/nsupdate.c

@@ -313,6 +313,7 @@ check_result(isc_result_t result, const char *msg) {
 static char *
 nsu_strsep(char **stringp, const char *delim) {
 	char *string = *stringp;
+	*stringp = NULL;
 	char *s;
 	const char *d;
 	char sc, dc;
@@ -340,7 +341,6 @@ nsu_strsep(char **stringp, const char *delim) {
 			}
 		}
 	}
-	*stringp = NULL;
 	return (string);
 }