clean the unittest2.
clean the unittest2.

We have used the testtools instead of unittest2. So when we run
tempest, if it require unittest2 packages. We should look into
why it need unittest2, and can we use testtools instead? Not just
add unittest2 in pip-require simply. And new test added into
tempest should use testtools other than unittest2.

Change-Id: Ica02779b16434f9d64b0bb655c44251301b94492

cneill/tempest-lib,JioCloud/tempest-lib,afaheem88/tempest-lib,mtreinish/tempest-lib,varunarya10/tempest-lib,sorenh/tempest-lib