select/cray - free all memory at shutdown

This just shuts down the underlying select plugin used by select/cray
in order for it to free all of its allocated memory
CRAY - fix issue with using CR_ONE_TASK_PER_CORE
replace old commit note erroneously taken out
CRAY - fix memory leak when using accelerators
Merge branch 'slurm-2.6'

Conflicts:
	src/plugins/select/cray/select_cray.c