Fix test breakage in vCard exporter.

Due to the change Iae8dbac1, all tests for vCard exporeter has failed.
This change fixes the breakage by using a kind of dirty Dependency Injection.

Current test framework for vCard exporter strongly depends on the assumption that
ContentValues objects are able to be directly passed to objects which use
ContentResolver, while the change above disabled the feature by removing
queryEntities().

This change makes VCardComposer forcibly uses queryEntities() via Reflection.
I agree that this change is not so clean, but works fine for now.