Add testpmd as vswitch class

Add testpmd as vswitch class

The purpose of using testpmd instead of OVS is to get the baseline
of the DUT when performing hardware offloading operations.
There are supported different checksum calculation
and txq flags settings.

Change-Id: I93c9b45dcb31eaa1f610b7e061f3dd5936b0e6ec
JIRA: VSPERF-193
Signed-off-by: Robert Wojciechowicz <robertx.wojciechowicz@intel.com>
Reviewed-by: Dino Simeon Madarang <dino.simeonx.madarang@intel.com>
Reviewed-by: Maryam Tahhan <maryam.tahhan@intel.com>
Reviewed-by: Brian Castelli <brian.castelli@spirent.com>