tcp tuning

http://chimera.labs.oreilly.com/books/1230000000545/ch02.html#_tuning_server_configuration

1-2 were already enabled by default, this does the third and fourth needs
newer kernel, which should come when we upgrade to 14.04 LTS later this year.

Change-Id: I6eecebf9aeadf71648421dff7684b000b309e763
Merge "tcp tuning"