Catchall for Heisenbug Sightings in SOS

[markbrown314]

These are rare bugs seen during unit tests that are difficult to reproduce.

Please provide build and environment details.

[markbrown314]

SOS unit test: shmem_team_max and c11_shmem_team_collective_types once on UCX v1.18 testing hang when UCX with multithreading support is enabled

UCX v1.18 config:
$ ./configure --with-go=no --prefix ${WORK_DIR} --enable-mt

SOS (5c52aa) config:
./configure --prefix=${WORK_DIR} --with-ucx=${WORK_DIR} --enable-pmi-simple

Intel(R) Xeon(R) Platinum 8480+
(single node local testing)

[markbrown314]

Here is one with mt_membar