Integrate vsperf in Tgen mode

Integrate vsperf in Tgen mode

Problem:
Running Vsperf in Tgen mode is supported but the integration is not complete at the code level
i.e. not ready-to-use, and dpdk loopback is not supported inside the VM.

Solution:
(1) Completely automates VM image generation and supports 1G huge pages.
(2) Adds a new test scenario VsperfDPDK for testpmd based loopback inside the VM.

Update 1-2: Fixed "line too long" issues not reported by local run_tests.sh (why?)
Update 3: Per comment change to use SSH.from_node() and add unit test cases
Update 4: Add more unit test cases for coverage and ready the code for merge

JIRA: YARDSTICK-661

Change-Id: Iea3014d4c83e1b0c079019a4ed27771d40a7eed8
Signed-off-by: Jing Zhang <jing.c.zhang@nokia.com>