Ignore Allow/DenyQOS in part if QOS not configured

Previous logic would fail an assert
Remove some v15.08 code

The perl API sbcast function included a step ID, which is NOT in v14.11, on v15.08
Perl API to return node MIXED state

Add new slurm_load_node flag of SHOW_MIXED, which will change a node's
state from ALLOCATED to MIXED by comparing the number of CPUs allocated
against the total CPU count on each node
bug 1209
Improve slurmctld error message

bug 1207
Merge branch 'slurm-14.03' into slurm-14.11
Merge branch 'slurm-14.11'