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

[Hefty, Sean]

Release candidate 1 for v1.5.4 is available from:

https://github.com/ofiwg/libfabric/releases/tag/v1.5.4rc1

Everything should be ready for release.  Provider maintainers please validate rc1, plus check the release notes (NEWS.md) and man pages.  The release notes have been updated.

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.

- Sean