Add missing VRT_handled() check to catch return from the callback sub

I wonder who has written the vmod.rst documentation clearly pointing out
that this needs to be done... :|

Ref Varnish-Cache ff18a3c5bf7cf02acaa5bc5672cc90c8bb805336

src/vmod_re.c

@@ -475,7 +475,8 @@ vmod_regex_foreach(VRT_CTX, struct vmod_re_regex *re, VCL_STRING subject,
 		return (0);
 
 	ov = (ov_t *) task->priv;
-	while (match(ctx, re->vre, subject, PCRE2_ZERO_TERMINATED,
+	while (! VRT_handled(ctx) &&
+	       match(ctx, re->vre, subject, PCRE2_ZERO_TERMINATED,
 		     ov->ovector[1], 0,
 		     task, get_limits(re, &buf, limit, limit_recursion))
 	       > PCRE2_ERROR_NOMATCH)
@@ -786,7 +787,8 @@ foreach_iter_f(void *priv, unsigned flush, const void *ptr, ssize_t len)
 #endif
 
 	i = reip_iter(reip, flush, ptr, len);
-	while (i == 0 && reip->s > PCRE2_ERROR_NOMATCH) {
+	while (i == 0 && reip->s > PCRE2_ERROR_NOMATCH &&
+	       ! VRT_handled(reip->ctx)) {
 		VRT_call(reip->ctx, reip->sub);
 		i = reip_iter(reip, flush, ptr, len);
 	}