Fix transcoding 'success' metric result

I68c33fbd0c88b67340d1042fed42b8fa00371a76 introduced a regression
where we always reported a transcoding session as failed even if it
might have been successful

Test: Manual
Bug: 182380285
Change-Id: Ia5224892db9e89c7b35dc74642c481ec2df976d3
1 file changed