Fix vader MPI_THREAD_MULTIPLE deadlock.

[jsquyres]

Discussed at Feb 2016 Dallas meeting. @bosilca says he runs into it periodically; he will get with @hjelmn and help identify where the problem is.

[jsquyres]

@bosilca Can you share this test? I'd like to add it to the Cisco MTT runs.

[bosilca]

It is a modified version of the osu_mbw_mr benchmark. The only real difference is that we are initializing the MPI library in MPI_THREAD_MULTIPLE mode.