Add OVS tunnel encapsulation performance test

Add OVS tunnel encapsulation performance test

Measure OVS DPDK and native VXLAN/GRE/GENEVE encapsulation performance.
This patch creates a new deployment scenario, Overlay_P2P.
The DUT is configured as a TEP (Tunnel Endpoint)
which performs encapsulation of frames and sends traffic to
the 2nd traffic generator port. The traffic generator in this
case receives an encapsulated frame. No decapsulation is performed
in this testcase.

Introduce a vsperf param, --run-integration, to filter tests to
integration tests. When running integration tests, variables defined
in the directory conf/integration/*conf as well as the conf/*.conf
are available.

This test case requires DPDK 2.1.0 and OVS master - 6bb4a18 or newer.

Change-Id: Ide2f418909d647119388df9b30d0d0a3656b4e53
JIRA: VSPERF-180
Signed-off-by: Dino Simeon Madarang <dino.simeonx.madarang@intel.com>
Reviewed-by: Maryam Tahhan <maryam.tahhan@intel.com>
Reviewed-by: Al Morton <acmorton@att.com>