The current script used ephemeral port range which clashed with the
ports used by the tools (dig, ...), and the range always started with
the first port and there was 100 ports allocated for each system test.
In this commit, the first port has been randomized, the get_ports.sh
script outputs the variables (the output has to be eval'ed from run.sh)
and there's less waste in the port range.
52683934cd