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
Merge "Replace tearDown with addCleanup - Part 5"