PR #5241 provided an MCA variable to allow multi-threaded opal_progress.
However, it allowed to update the linked list even when multiple threads was
allowed to call opal_progress. This caused a scenario when a more recent thread
could complete it's progress and fail the assert(sync ==
wait_sync_list).
Allowing to update the linked list only for the case when the number of threads
exceeds the threshold fixes the problem.
Signed-off-by: Aravind Gopalakrishnan <Aravind.Gopalakrishnan@intel.com>