Replace tearDown with addCleanup - Part 5

Replace tearDown with addCleanup - Part 5

Replace tearDown with addCleanup in:
- cinder/test.py
- cinder/tests/test_migrations.py

Remove empty tearDown methods from:
- cinder/tests/test_hp3par.py
- cinder/tests/test_hplefthand.py
- cinder/tests/test_ibmnas.py
since it does not add any functionality (and empty setUp methods as well).

Infra team has indicated that tearDown should not be used and should
be replaced with addCleanup in all places.

Implements blueprint replace-teardown-with-addcleanup

Change-Id: Id2fdd3e2e1ab8458083697b6ea6714ca019fd00a