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