libfabric: update to ofiwg/libfabric@8da3957de326e6fa2164af71059c04263037e678

Pull down a new embedded copy of libfabric from
https://github.com/ofiwg/libfabric.
libfabric: update embedded libfabric configury

To support the newly-copied libfabric downloaded from github
ofiwg/libfabric@8da3957de326e6fa2164af71059c04263037e678.