orchestration API base class rename clear* functions

Rename the clear* functions as they are "private" and only called
in tearDownClass - being effictively garbage collectors for the test
class we want to make clear that these should not be called from
the tests themselves.

Change-Id: I8b022a730af981ca202fe9f190d91ef9af3bf92d
Merge commit 'refs/changes/65/81565/4' of git://gold.eng.hq.xensource.com/git/github/openstack/tempest into tmpbranch