power/cray developments

Remove time from "capmc get_node_energy_counter" call. If no recent
  data is available, no data is being returned, so just get latest
  information.
Initialize a variable to avoid xfree of uninitialized variable.
Correct joule to watt calculation (">" changed to "<")
Read configuration once when slurmctld starts rather than twice
Compute a node's power consumption with more precision based upon
  time to the microsecond