Fix for issue 787: Extra 2ms delay in OSBA STEREO output

EVS 26.444 BE test passes.
pytests results: 597 failed, 381 skipped

MLD scores:
Original inputs:
MLD > 10: 64
MLD > 5 : 128
MLD < 5 : 405

+10dB inputs:
MLD > 10: 193
MLD > 5 : 199
MLD < 5 : 205

-10dB inputs:
MLD > 10: 24
MLD > 5 : 75
MLD < 5 : 498