hash table UPDATE optional cb for HT free

Allows freeing items in the hash table.
diff --git a/tests/utests/basic/test_hash_table.c b/tests/utests/basic/test_hash_table.c
index 25b595a..3e07bef 100644
--- a/tests/utests/basic/test_hash_table.c
+++ b/tests/utests/basic/test_hash_table.c
@@ -96,7 +96,7 @@
     assert_int_equal(LY_ENOTFOUND, lyht_remove(ht, &i, i));
     CHECK_LOG("Invalid argument hash (lyht_remove_with_resize_cb()).", NULL);
 
-    lyht_free(ht);
+    lyht_free(ht, NULL);
 }
 
 static void
@@ -153,7 +153,7 @@
     }
 
     /* cleanup */
-    lyht_free(ht);
+    lyht_free(ht, NULL);
 }
 
 static void
@@ -253,7 +253,7 @@
         assert_int_equal(rec->hits, 0);
     }
 
-    lyht_free(ht);
+    lyht_free(ht, NULL);
 }
 
 int