[BUG] stream_sock: fix handling for server side PROXY protocol

Patch 5ab04ec47c9946a2bbc535687c023215ca813da0 was incomplete,
because if the first send() fails on an empty buffer, we fail
to rearm the polling and we can't establish the connection
anymore.

The issue was reported by Ben Timby who provided large amounts
of traces of various tests helping to reliably reproduce the issue.
1 file changed