Tests use cleanUp rather than tearDown

The tests were putting clean-up code in tearDown. Using tearDown
causes problems with developing and testing because if there's an
exception raised in setUp then tearDown is not called and this
can affect other tests and make it hard to figure out what the
problem was.

Also, this should make it easier to switch to using fixtures since
fixtures use cleanUp.

Change-Id: Ifc22dfd9012402c895a09534f4b1d9bd7a2ec931
Merge "Tests use cleanUp rather than tearDown"
Use HTTPretty in S3 test code

Remove the httplib specific mocks that are used within the S3
middleware. This won't work when we convert S3 middleware to use the
requests library.

Change-Id: Iee5f3089286c980bef3a19dc9d5068399946e217
Related-Bug: #1275598