Remove code for multiple OOB progress threads as it is an optimization
nobody uses. Also turns out to have a race condition that can cause
segfault on finalize, so maybe good that nobody is using it.
Signed-off-by: Ralph Castain <rhc@pmix.org>
(cherry picked from commit 41eb41c3f224abcacec78f4d77c138197c36f172)
(cherry picked from commit a2f35c1834ab2fcb216285621d177a179e33dfe7)