Tests: Clean up PUSH IN MIDDLE in master_stream test
Tests: Clean up PUSH IN MIDDLE in master_stream test

We weren't silencing the normal FileSource emit, so it was pushing unexpected
data during our test.

StreamMachine/StreamMachine,pteich/StreamMachine,SCPR/StreamMachine,pteich/StreamMachine,StreamMachine/StreamMachine,cdgraff/StreamMachine,cdgraff/StreamMachine,SCPR/StreamMachine,pedropapa/StreamMachine,pedropapa/StreamMachine,DreamNetwork/StreamMachine,DreamNetwork/StreamMachine