Do not treat lack of mpi_fini as error

Log Cray MPI job calling exit() without mpi_fini(), but do not treat it as
a fatal error. This partially reverts logic added in version 14.03.9.
bug 1171
Merge branch 'slurm-14.03' into slurm-14.11

Conflicts:
	src/plugins/task/cray/task_cray.c