Fix an SST stream servicing call.
Fix an SST stream servicing call.

If we possibly generate multiple packets for a write call, we should
check that at least one packet was successfully added before
scheduling the stream for servicing.

sirikata/sirikata,sirikata/sirikata,sirikata/sirikata,sirikata/sirikata,sirikata/sirikata,sirikata/sirikata,sirikata/sirikata,sirikata/sirikata