- Removed pf_remove_src_node().
- Introduce pf_unlink_src_node() and pf_unlink_src_node_locked().
These function do not proceed with freeing of a node, just disconnect
it from storage.
- New function pf_free_src_nodes() works on a list of previously
disconnected nodes and frees them.
- Utilize new API in pf_purge_expired_src_nodes().
In collaboration with: Kajetan Staszkiewicz <kajetan.staszkiewicz innogames.de>
Sponsored by: InnoGames GmbH
Sponsored by: Nginx, Inc.