Merge new test infra changes from bhushana/contrail-test

Below set of changes are targeted to achieve the following
* Better organization of test suites and utilities for easier use
* Ability to run tests in parallel as well as in serial mode
* Enhanced reporting and logging
* Results to be stored in result.xml in Junit Test report format
to be later readable by tools like Jenkins

More details on running these tests can be found at
https://github.com/Juniper/contrail-test/wiki/Running-tests-in-parallel
Another example :
https://github.com/Juniper/contrail-test/wiki/Running-Neutron-API-Tests

Change-Id: If16dd040894ad02096b570ddc558d3a9646c6769