[ofiwg] completion flags as actually defined by OFI

[Hefty, Sean]

> > 'the results of the operation are visible to all observers, including
> > the target's CPU'
> 
> Part of the semantic that needs to be captured is that the target process
> _may_ need to take additional steps in order to access the data.  For
> example, the process may need to provide a buffer that the data can be
> placed into.  I was intentionally vague on the meaning of 'visible',
> because that is provider/operation/target specific.

The word 'available' is a better choice.