fix checking unit test

git-svn-id: https://svn.code.sf.net/p/libtorrent/code/trunk@10418 a83610d8-ad2a-0410-a6ab-fc0612d85776
fix test_checking

git-svn-id: https://svn.code.sf.net/p/libtorrent/code/trunk@10419 a83610d8-ad2a-0410-a6ab-fc0612d85776
transition tracker_connections to use shared_ptr instead of intrusive_ptr. optimize udp tracker connection lookups by using unordered map instead of linear search.

git-svn-id: https://svn.code.sf.net/p/libtorrent/code/trunk@10420 a83610d8-ad2a-0410-a6ab-fc0612d85776