MEDIUM: listener: fix polling management in the accept loop

MEDIUM: listener: fix polling management in the accept loop

The accept loop used to force fd_poll_recv() even in places where it
was not completely appropriate (eg: unexpected errors). It does not
yet cause trouble but will do with the upcoming polling changes. Let's
use it only where relevant now. EINTR/ECONNABORTED do not result in
poll() anymore but the failed connection is simply skipped (this code
dates from 1.1.32 when error codes were first considered).