Latency performance test

[ifilippov]

What is speed parameter? Can you please make this test more actual.

[ifilippov]

Also you should change this test to generate some files (with modified perf_compare) which can be compared with previous ones.

[just-musha]

Current test is in my branch https://github.com/intel-go/nff-go/tree/mbulatova/latency Added scope according to perf.json (perf_main, perf_light, perf_seq) Takes 34m to complete

[just-musha]

After #353 is implemented, writing to files will not be necessary

[ifilippov]

We need measurable and comparable latency results