capture: Traffic capture examples

capture: Traffic capture examples

Traffic can be captured also at DUT side. Two options are supported by
vsperf:
1) Traffic is captured inside VM after it has been processed
   by vSwitch. This can be used for verification of vSwitch frame
   modification functionality, including HW offloading at ingress side.
2) Another NIC under the test (NIC2) is added into standard VSPERF DUT
   setup. Traffic is then forwarded from TGen through NIC and vSwitch
   to NIC2 and then over patch cable back to NIC2, the vSwitch, NIC and
   to the traffic generator. This setup supports also verification of HW
   offloading at egress side of NIC2 and thus it can be used for validation
   of smart NICS.
Both options above are traffic generator agnostic if compared to direct
support of traffic capture by traffic generator. This patch introduces
example testcases for both options.
Detailed documentation will be pushed as a standalone patch.

JIRA: VSPERF-556

Change-Id: I23e12e45768ae4dbe9442f74d8391c3d5b2c7895
Signed-off-by: Martin Klozik <martinx.klozik@intel.com>
Reviewed-by: Richard Elias <richardx.elias@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>