Improve IXIA IxNetwork library and traffic profile (1)

Improve IXIA IxNetwork library and traffic profile (1)

This patch introduces a new way to configure the TCL IxNetwork server.
All the configuration is done using the TCL API, removing the need of
using the pre-saved configuration file.

"IxNextgen.assign_ports" creates and assigns the virtual ports for each
physical port defined in the test case.

"IxNextgen.create_traffic_item" creates one traffic item and two flow
groups per pair of ports, in both directions.

"IxNextgen.gt_statistics" retrieves only the required statistics to
generate the samples blob in the traffic generator.

JIRA: YARDSTICK-1116

Change-Id: I8f1c0c55e99c274b2ed8276ed9a385c502e16d93
Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>
Signed-off-by: Emma Foley <emma.l.foley@intel.com>