CHO TEST

Summary:
        This is a long-term regression test that is aimed to run
        for weeks at a time. It's goal is to find memory leaks or bugs that
        otherwise cannot be easily seen with short-term tests. The following
        is an overview of the steps that are performed in this test.
        Steps:
        - Discover IPv4 and IPv6 hosts
        - Add host intents
        - Ping all hosts
        - Bring links down
        - Ping all hosts
        - Bring links back up
        - Ping all hosts
        - remove intents

        These steps are iterated over and over again. The number of iterations can
        be found in the params file.

Topology:
        Att topology - 25 switches and 25 hosts and its structure is designed to simulate
                        a real world configuration,
        Chordal topology - 25 swithces and 25 hosts and because of its chordal graph structure,
                            it's particulary useful in testing the rerouting capability of ONOS.
        Leaf-spine topology - 78 switches and 68 hosts and designed to simulate modern data centers.

Pre-requisites:
        To run out-of-the box this test requires 3 NODES. The cell file
        must be passed through the startup test command, e.g.,

            ./cli.py run CHOtest onoscell <cell name>.

        Passwordless login must be set from TestStation "sdn" root user.
        This test relies on the topology files to start Mininet located in
        the dependencies folder. Be sure to check that each topology file can
        be loaded properly by Mininet by using this command:

            sudo ~/<dependencies path>/<topology name>