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).
Merge pull request #67 from jsquyres/pr/revert-thread-lock-enable-by-default

Revert most of open-mpi/ompi@6ef938de3fa9ca0fed2c5bcb0736f65b0d8803af

Conditional on review of test results