netdetect: Adding server's list in output

When reading at output later, it's really important to get the context.
As network performance is realted to other hosts too, providing the
complete list of servers involved during the benchmark is useful to
understand what servers got used during this benchmark session.

A typical output is :
 ('network',
  'tcp_bench',
  'hosts_list',
  "[('d8:9d:67:1a:41:7c', '10.66.6.247'),
    ('d8:9d:67:1a:8f:58', '10.66.6.245'),
    ('d8:9d:67:1a:9b:1c', '10.66.6.248')]"
 )