Do we *require* RDMACM support in the openib BTL?

[jsquyres]

In v2.0.x and v2.x, we no longer have the oob CPC in the openib BTL.

Do both the RDMACM and UDCM CPC's require IPoIB support?

This is inspired by a question from the mailing list: https://www.mail-archive.com/users@lists.open-mpi.org/msg30223.html

If we now require IPoIB support for correct openib BTL functionality, that needs to be documented somewhere (probably in README and the FAQ).

[jsquyres]

Note: I just re-forumlated the question in this issue -- I originally asked a slightly different question (about requiring RDMACM support vs. requiring IPoIB support).

[jsquyres]

We discussed on the call today: IPoIB is not required for the openib BTL. Specifically: the UDCM CPC does not require IPoIB. @hjelmn will follow up with the user on the list to see why UDCM was deselecting itself.