Bug fixing: race condition in stream close/replace
 - in Lpel_hrc: stream close reset the prod_sd/cons_sd to NULL (so that
   the task can update its neighbor list). Stream replace also set a new
   prod_sd/cons_sd --> used lock and check if stream is repalced already
   then no need to set to NULL.
 - remove these features from lpel_decen as it does not use dynamic
   priority based on stream fill level
add radom priority function (13) for lpel hrc