network: tcp_fastopen: add TCP Fast Open test

This is a perfomance test for TCP Fast Open (TFO) which is an extension to
speed up the opening of TCP connections between two endpoints. It reduces
the number of round time trips (RTT) required in TCP conversations. TFO could
result in speed improvements of between 4% and 41% in the page load times on
popular web sites.

The default test scenario simulates an average conversation between a
web-browser and an application server, so the test results with TFO enabled
must be at least 3 percent faster.

The test must be run on Linux versions higher then 3.7. (TFO client side
implemented in Linux 3.6, server side in Linux 3.7).

Signed-off-by: Alexey Kodanev <alexey.kodanev@oracle.com>