Actually pay attention to the kqueue flags that we need to use.

This fixes some read/write flags behaviour where it wasn't being treated
as a one-shot event and would just keep wasting CPU triggering the
event until we handled it.
Disable doing client-side sending netbuf allocations for now, we aren't
sending and it's thus a waste of time.
Merge branch 'master' of github.com:erikarn/libiapp