pdt(k): made the "bad parameters" diagnostic in pdt_get_domain INFO

- I observed this message a few times while playing around with PDT.  It isn't
  really an error as it occurs when sdomain is NULL and sdomain does not have
  to be set at all.  Changed it to INFO for now.

modules_k/pdt/pdtree.c

@@ -294,7 +294,7 @@ str* pdt_get_domain(pdt_tree_t *pl, str* sdomain, str *code, int *plen)
 	if(pl==NULL || sdomain==NULL || sdomain->s==NULL || code == NULL
 			|| code->s == NULL)
 	{
-		LM_ERR("bad parameters\n");
+		LM_INFO("bad parameters\n");
 		return NULL;
 	}