ixia: Support of 1 NIC connection to trafficgen

ixia: Support of 1 NIC connection to trafficgen

For some testcases it is useful to have only one connection between
traffic generator and DUT. Thus IxNet class was extended to support
such connection. Feature is enabled if both IXIA ports are set to
the same value.
New integration testcase ixnet_pvp_tput_1nic was created to demonstrate
this feature.
Unused code was removed from 3rd_party/ixia/ixnetrfc2544.tcl to simplify
introduction of new features and to speed up IXIA configuration.

JIRA: VSPERF-503

Change-Id: I92ab24fa58eeb1ccb7f00ac7f3530ffca7b99241
Signed-off-by: Martin Klozik <martinx.klozik@intel.com>
Reviewed-by: Al Morton <acmorton@att.com>
Reviewed-by: Christian Trautman <ctrautma@redhat.com>
Reviewed-by: Sridhar Rao <sridhar.rao@spirent.com>
Reviewed-by: Trevor Cooper <trevor.cooper@intel.com>