Clean up step on a failed node correctly.

This patch does 2 things:
1. When a step fails on some node, then mark it as complete on those
   nodes. This is needed so that when the step ends on the other
   nodes, slurmctld recognized the step as completely done.
2. If the step does not have the --no-kill option set, then when some
   node fails, send a request to terminate the step on ALL of its nodes.

Bug 5805