JSONDictSerializer encode objects to unicode

Averts raising ValueError, Circular Reference Detected exception.
Add additional test to JSONDictSerializerTest testing that
JSONDictSerializer correctly serializes objects into unicode repr.
and not raise error
Fixes: bug #1089100

Change-Id: Ifdb0562c7c43ab66617dddb65f16f893df2f4895
Merge "JSONDictSerializer encode objects to unicode"