CSIT-102: Add latency measurement to performance testing

CSIT-102: Add latency measurement to performance testing

- Add latency stream as a background stream in both directions
- Latency background stream is not using the VM transformation engine.
  Raw stream with single packet is created.
- Latency background stream has 1kpps rate with packet of same size as
  traffic stream.
- Display latency values (min/avg/max) in results of TC and reporting
  remaining data including histogram and jitter inside of the
  search/pass keyword.

Change-Id: I78ce4659b57caab08d5729f51a1e14d518fd3273
Signed-off-by: Peter Mikus <pmikus@cisco.com>
Signed-off-by: pmikus <pmikus@cisco.com>