Correct job dependency string

Correct logic returning remaining job dependencies in job information
reported by scontrol and squeue. Eliminates vestigial descriptors with
no job ID values (e.g. "afterany"). As depdencies are removed, the
job ID values were removed from the strings, but not the descriptors.
This eliminates both. It also checks the full job ID to make sure we do
not remove "afterany:1234" when job "123" completes.
Merge branch 'slurm-2.6'

Conflicts:
	src/slurmctld/job_scheduler.c