portals4: add support for dynamic add_procs() to all Portals4 components

[tkordenbrock]

In the default mode of operation, the Portals4 components support
dynamic add_procs().

The Portals4 components have two alternate modes (flow control and
logical-to-physical) that require knowledge of all procs at startup.
In these modes, mtl-portals4 or btl-portals4 iterates through all
the procs in MPI_COMM_WORLD to allocate them and create the
endpoints.

@hjelmn - Please review the use of ompi_group_get_proc_ptr_raw()
and ompi_proc_for_name() in mtl_portals4.c.

[hjelmn]

There should be no calls to ompi from opal. I see what you need. Let me see if there is a way to do it without ompi calls. If not I will see what I can provide that will give you what you need.

[hjelmn]

@tkordenbrock @regrant I will be in Albuquerque for part of day tomorrow. If any face-to-face time to discuss the add_procs changes would help let me know.

[tkordenbrock]

@hjelmn @regrant Thanks for the offer, but I won't be in Albuquerque tomorrow. I think I should have an updated PR #906 (or create a new one?) ready today. The only question I have is how to do the PRs since my work here will depend on your PR #929.

[hjelmn]

@tkordenbrock Please comment on #929 to add to the discussion. I can probably commit that one tomorrow since it is the only way to 1) respect project boundaries, and 2) not add the notion of the world size to opal. For now please open a PR on my add_procs branch. That way I can evaluate it all together and then merge to automatically update #929.

[tkordenbrock]

Superseded by PR #929. Closing.