[ofiwg] libfabric v1.5.4rc1 and v1.6.2rc1 updates

[Hefty, Sean]

> v1.6.2rc1 should be ready within the next day or so.  I'm going to re-
> spin the (unreleased) package to pull in a recent fix.  For 1.6.2, I
> need the provider maintainers to update NEWS.md.

v1.6.2rc1 is now available:

https://github.com/ofiwg/libfabric/releases/tag/v1.6.2rc1

The NEWS.md updates are still needed prior to the final release.

- Sean