[ofiwg] fi_trywait and providers

[Hefty, Sean]

The 1.3 libfabric release will contain the fi_trywait call.  For providers, there are a couple of options available for handling this.

- The libfabric core can check that a provider supports the 1.3 API, and reject those that don't.  This is the easy button.

- The fi_trywait call can include a check against the provider's fabric ops to see if trywait was implemented.  This conditional check would be in all fi_trywait paths.

- The libfabric core can wrap the provider's fabric ops with its own copy of fabric ops.  This requires mapping the provider's fabric fid to a core fabric fid for the sake of compatibility.  This is only needed for providers asking for API < 1.3.  This is the hard button.

- Sean