fix issue with obfuscated_get_peers where peers in responses to obfuscated requests would still be returned. slight refactoring to move traversal algorithm level logic to traversal_observer class

git-svn-id: https://svn.code.sf.net/p/libtorrent/code/trunk@9405 a83610d8-ad2a-0410-a6ab-fc0612d85776