node_features/knl_cray: add UME monitoring

Add logic to monitor Uncorrectable Memory Errors (UME) and notify
  active jobs in case they run for a while afterwards. This copies
  logic from knl_generic to knl_cray. There may be a different UME
  monitoring system for Cray systems in the future. The original
  knl_generic development is in commit 56ff27da
bug 3341