rb was relying on client.List() to find all elements that needs to be
removed. However it doesn't include 'alias/bucket' in the listing
when 'alias/bucket' itself is passed as an argument in rb command.
This PR will always attempt to delete the passed argument as this is
what the user wants in the first place.
This PR also fixes teardown() in functional-tests.sh to remove
the bucket using rb instead rm since rm does not remove buckets
anymore.
