sibling clusters.

back a message to the caller.

a federation connection, someone adding and removing the cluster
from the federation lots of times at the same time the cluster could
be not found.

Fixes build issue caused by 844830d4.

connection

error.

at startup.  Starting it up when you get a connection from another
cluster could cause delays in processing the request.

want to only wait for message_timeout instead of forever.  Otherwise
we could hit deadlock if the other person is trying to do the same
thing.

processed at a time.  Otherwise you could get issues if you are
rapidly adding and removing a cluster from a federation.  Probably
not likely in real life, but in testing that is a different story.

slurmctld.

scenario when first added to a federation.

the same logic that was found in the slurmdbd.  Now both functionalities
share the same code.

This was done with the merge right before this commit.

update is sent to a slurmctld.

with real persistent connections.

the fd is set to -1 so we don't try to actually use it.

when querying if there are runaway jobs.

out in, but it is back now!

The old logic isn't needed anymore since we spawn a new thread.