merged completed-on fix from RC_0_16

git-svn-id: https://svn.code.sf.net/p/libtorrent/code/trunk@9274 a83610d8-ad2a-0410-a6ab-fc0612d85776
restore web_server.py

git-svn-id: https://svn.code.sf.net/p/libtorrent/code/trunk@9275 a83610d8-ad2a-0410-a6ab-fc0612d85776
fix race condition of closing http socket in web_server.py

git-svn-id: https://svn.code.sf.net/p/libtorrent/code/trunk@9276 a83610d8-ad2a-0410-a6ab-fc0612d85776
fix ssl issue in web_server.py

git-svn-id: https://svn.code.sf.net/p/libtorrent/code/trunk@9278 a83610d8-ad2a-0410-a6ab-fc0612d85776
fix web_seed_chunked test

git-svn-id: https://svn.code.sf.net/p/libtorrent/code/trunk@9280 a83610d8-ad2a-0410-a6ab-fc0612d85776