src/hooks/dhcp/high_availability/ha_messages.mes
    HA_SERVICE_CONNECT_INVALID_SOCKET - new message

src/hooks/dhcp/high_availability/ha_service.cc
 HAService::clientConnectHandler() - added negative fd logic

src/lib/http/client.cc
    Connection::closeCallback() - new method that wraps invocation
    of close callback in try-catch.

src/lib/http/http_messages.mes
    HTTP_CONNECTION_CLOSE_CALLBACK_FAILED - new message