need PR 6855 pushed back to release branches

[hppritcha]

PR #6855 needs to be merged back in to v4.0.x, v3.1.x, and v3.0.x

[jsquyres]

@hkuno As discussed on 2019-08-27 webex, if these PRs get in in the Very Near Future, they can be part of v4.0.2.

[hppritcha]

PR #6946 clears label 4.0.x

[hkuno]

I'm sorry it is taking me so long to submit the PRs for v3.0.x and v3.1.x.
While we can show that we can hit the issue in 4.0.x by using ucx over IB with "--mca pml_ucx_opal_mem_hooks true", we aren't sure if this works in earlier builds, and it is taking time to reproduce this issue in v3.0.x and v3.1.x.

[jsquyres]

@hkuno Did this turn out to be unnecessary on v3.0.x / v3.1.x?

[hppritcha]

closing this as we don't plan to release updates to 3.0.x and 3.1.x