Replace tearDown with addCleanup - Part 4

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

All addCleanup methods will be executed even if one of them fails, while
a failure in tearDown method can leave the rest of the tearDown un-executed,
which can leave stale state laying around.

Moreover, tearDown methods won't run if an exception raises in setUp method,
while addCleanup will run in such case.

This patch replaces tearDown with addCleanup or removes redundant tearDown
methods in cinder unit tests.

Implements blueprint replace-teardown-with-addcleanup

Change-Id: I6947eafa419ed7dda53582484090cd5210274f73
Merge "Replace tearDown with addCleanup - Part 4"