First attempt at pinging that doesn't really work well.
Do the pinging in a separate process so we don't block the node monitor.
Use a macro
Don't call rabbit_mnesia:cluster_nodes(all) as much, don't use floating point if we don't have to.
Merged bug25491 into default
Merge in default, add a touch more logging, and don't restart autoheal if it's already started.
Cosmetic