Based on work from usNIC, the best way to use the reachability
information the reachable components return is to build a
connectivity graph between the two peers and run a bipartite
graph solver. Rather than returning the "best" pairing,
the reachability framework now returns the entire mapping,
allowing a (soon to be added) graph solver to build the
"optimal" connectivity pairing.
Practically, this means changing the return type of the
reachable() function and rewriting the weighted_reachable()
function to return the full mapping. The netlink_reachable()
function still always returns NULL.
At the same time, fix bit-rot in the weighted component and
enable builds of the component by removing the opal_ignore.
Also, add IPv6 support to the weighted component to support
both use cases in the TCP BTL.
Signed-off-by: Brian Barrett <bbarrett@amazon.com>
