In test assertion failure messages the DUMMY_VALUE would be shown as
<object object ...> which is not immediately recognisable as the dummy
value..
This change makes the DUMMY_VALUE show as
<test.unit.common.middleware.helpers.FakeSwiftDummyValue object ...>.
Change-Id: I73fac245c65c48d45e4919c6f15688d482148407
Related-Change: I332ce724aa10287800cbec8ca21aacc3bbd3c22a