[#2647] Respect IOV_MAX when call writev in native transport

Motivation:

epoll transport fails on gathering write of more then 1024 buffers. As linux supports max. 1024 iov entries when calling writev(...) the epoll transport throws an exception.

Thanks again to @blucas to provide me with a reproducer and so helped me to understand what the issue is.

Modifications:

Make sure we break down the writes if to many buffers are uses for gathering writes.

Result:

Gathering writes work with any number of buffers