add maintenance script to retry failed transcodes

i.e to retry all transcodes that failed in
av_interleaved_write_frame before it this
was fixed with libvpx update:

php retryTranscodes.php \
 --error "av_interleaved_write_frame(): Invalid argument"

Change-Id: I41b8d905716423da513d16074de3b388eae05cce
Merge "add maintenance script to retry failed transcodes"