Revert most of open-mpi/ompi@6ef938de3fa9ca0fed2c5bcb0736f65b0d8803af

We only intended to bring over the "remove --enable-ompi-progress-threads" stuff, but instead brought over all the stuff to enable thread locking by default (which should only be on master, not over here on the v1.8 branch).

Hence, this commit reverts all of the above-mentioned commit *except* the --enable-ompi-progress-threads stuff (i.e., we still leave that stuff deleted from the v1.8 branch).

@hjelmn please review