msdkenc: break out of flush frames loop on error
In general, we should assume any unhandled error is non-recoverable.
In the flush frames loop, some error states can cause us to never increment the task and therefore we get stuck in an infinite loop and generate GST_ELEMENT_ERROR over and over again. This eventually consumes all system memory and triggers OOM. Thus, assume the worst and break out of the loop upon the first "unhandled" error.
Closes #859 (closed)