Fix AVL tree traversal in cache_record_find and cache_host_is_known

Fix AVL tree traversal in cache_record_find and cache_host_is_known

The AVL tree traversal in both functions systematically misses the last
AVL tree element. This can lead to duplicate cache entries and lookup
failures.

The fix duplicates the correct AVL tree traversal approach of
cache_dump_recursive().

Signed-off-by: Martin Röder <[email protected]>
Signed-off-by: Felix Fietkau <[email protected]>