When test_objects run, it will load some dummy objects such as Foo
etc, the problem is that Foo did not have '_type' field, so the
unit test will be failed.
This patch was resetting objects for all test cases in test_objects.
Closes-Bug: #1413144
Implements part of bp increase-test-coverage
Change-Id: I84067db21cb087c2694145a5a733d867422b73a5