OPTIM: listeners: use tasklets for the multi-queue rings

OPTIM: listeners: use tasklets for the multi-queue rings

Now that we can wake up a remote thread's tasklet, it's way more
interesting to use a tasklet than a task in the accept queue, as it
will avoid passing through all the scheduler. Just doing this increases
the accept rate by about 4%, overall recovering the slight loss
introduced by the tasklet change. In addition it makes sure that
even a heavily loaded scheduler (e.g. many very fast checks) will
not delay a connection accept.