Fails to build with Boost 1.70 (Beta1)

[jbeich]

Regressed by boostorg/asio@a72fbb0b867f:

src/cli/tls_http_server.cpp:438:31: error: no member named 'get_io_service' in
      'boost::asio::basic_socket_acceptor<boost::asio::ip::tcp, boost::asio::executor>'
                   m_acceptor.get_io_service(),
                   ~~~~~~~~~~ ^
src/cli/tls_proxy.cpp:373:31: error: no member named 'get_io_service' in
      'boost::asio::basic_socket_acceptor<boost::asio::ip::tcp, boost::asio::executor>'
                   m_acceptor.get_io_service(),
                   ~~~~~~~~~~ ^