netdetect: Implementing network benchmarking

This pretty long commit is adding the following steps:
- compute the port list that every server shall create
- every server starts its benchmark servers
- every server inform the leader it's ready to run
- leader waits all servers to tell they are ready
- leader sends a message to start the benchmark
- servers runs the benchmark simultaneously

TODO:
- doing a precise configurtion of the benchmark
- parsing netperf's output
- save information