which agents are attached to which node, so that we can assign
portnumbers to them. Also add code to updating the DB with these
agents (virt_trafgens).

sim.tcl: Get rid of $pid_$eid_events (per experiment events table),
and replace with global eventlist table. Revisit this later, since it
was causing problems and we do not really have a problem right now.
Maybe later.

traffic.tcl: Add virt_trafgens DB table update code. Get rid of oskit
based traffic generators and replace with FreeBSD nodes, which will
boot up and check if they are traffic gen source. Add get_params call,
called by the event code im sim.tcl to get the current params for the
START event.