xgroup_set_param() avoids the string parsing overhead and
should be used instead.

Save re-parsing the input string back into the components.

Since ReleaseAgent is no longer required, we can strip out
all the supporting logic for it.

Accidentally removed bracked in checked-in code

If the network path to shared storage used for the StateSaveLocation
is separate from that used to communicate with the cluster, both the
primary and backup controllers can end up acting as master on loss
of the cluster network.

Alter the HA takeover code path to make sure that the job state
save file is not still being updated by the primary slurmctld.
If it is, refuse to takeover and retry again later.

Bug 3592.

Bug 3921.

Bug 4062.

Bug 4084

bug 3824

Do not run the Node Health Check on termination of the external
  step as this happens when the job allocation ends and the job
  NHC will be executed anyway.
Bug 4074

instead of waiting till end of script.

Bug 1286

Bug 4066
Bug 4135

This creates an empty directory, since we no longer bother
copying the job script or environment as of 28b7f853.