Made obsolete by moving the federation to an async model.

Don't need it anymore. Was used to hosw communications between sibling
clusters.

Previously it was only opening the connections at startup and then if
had something to send to a sibling that it didn't have a connection to.
It's better to have them establish the connection when the cluster is
added to the federation so that it can detect if the cluster is down
later and the clusters can sync jobs when joing the federation.

Since moving to a asynchronous model for submitting jobs in the
federation, LLC doesn't apply anymore. And since LLC was the only flag,
don't display the federation flags in outputs by default anymore.
Leaving the variable in the struct in case it is needed later.

Doesn't apply anymore now that federation communication is asynchronous
and jobs are submitted to all siblings without regards to a cluster's
weight.

I cannot fathom why this was added - this would only have
influenced something if listen() was implemented as an inline
function or a macro, which I don't believe has ever been the
case.

Regardless, on modern Linux systems that limit is set dynamically
through /proc/sys/net/core/somaxconn.

While not POSIX compliant, BSD and Linux platforms have shipped this
function for a long time, and slurmctld/slurmdbd/slurmd have actually
been using the version from libc instead of this local redefinition.

Zero cleanup functions exist within the source, remove all this
dead infrastructure.

bug 3822

Missed sreport in d3ee28fa

Forgot to add the .h changes.
1d20fe77

because it can't get the fed job lock from the origin cluster.

Only storing existing pointers so don't destroy them.

Only realloc and copy if there is something to copy in.

Coverity CID:169529

The sibling should send its job list even it is empty so that the other
sibling can see if any jobs are missing.

Coverity CID:169530, 169531

Bug 3708

Bug 3815

not being able to deal with pn_min_memory being a uint64_t.  Scripts are
urged to change to these new variables avoid issue.  If not set the
variables will be 'nil'.

Bug 3681

In 17.11(or other future version) we should move a lot of this common
code into a new lib.  The reason I didn't put these common changes
into common/xlua.c was because then I would have to link common to
liblua which I really didn't want to do.

In order for scancel -u <user> to be able to cancel jobs by user that
exist only on other clusters in the federation, scancel needs to load
all of them.

Running jobs can happen out of order.