Issue in testcase with CAS Combiner

[mac-op]

Description
Upon reviewing the UIMA spec for CAS Multiplier we realized the test case for CAS Combiner in test_engine.cpp is wrong, and the input CASes to the Combiner should continue along the pipeline (the default behavior), instead of being dropped. This means that there should be 4 output CASes instead of 2.

Fixes
A simple fix could be to change the number of expected outputs and the related assertions. Further discussions may be required.