Break up convert_obj

This patch simply breaks up the convert_obj method into 3 different methods
_populate_translator_data_(vdict|hdict|list) so this method is more
manageable. Further refactoring will come later.

Partially implements blueprint refactor-datasource-driver-framework

Change-Id: Ib5428a908995f795896233f5522c570efa0fea95
Merge "Break up convert_obj"