If using the sched/builtin plugin for FIFO scheduling, then do not
create an intermediate job queue to be sorted, but iterate directly
over the job list.

plugin specific

Conflicts:
	src/common/slurm_accounting_storage.c
	src/common/slurm_auth.c
	src/common/slurm_jobacct_gather.c
	src/common/slurm_priority.c
	src/common/slurm_topology.c
	src/slurmctld/sched_plugin.c

This is a backport of plugin initialization logic made in the
select/serial branch that we want to have in SLURM v2.4 and not
only in v2.5. Note the plugin logic in v2.5 is different and
this changes to not apply

Previous code could result in invalid memory reference.