ixia: Fix IXIA in trafficgen mode

ixia: Fix IXIA in trafficgen mode

There are two IXIA wrappers in VSPERF - IxNET and Ixia. It has
been found that legacy Ixia implementation is no longer working
in trafficgen mode. This issues has been fixed.

JIRA: VSPERF-513

Change-Id: Ief1db71f688a19c5b41508617ccbc73024a02c48
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>