scheduler: set job on system stack for CSI feasibility check

When the scheduler checks feasibility of each node, it creates a "stack" which
carries attributes of the job and task group it needs to check feasibility
for. The `system` and `sysbatch` scheduler use a different stack than `service`
and `batch` jobs. This stack was missing the call to set the job ID and
namespace for the CSI check. This prevents CSI volumes from being scheduled for
system jobs whenever the volume is in a non-default namespace.

Set the job ID and namespace to match the generic scheduler.

scheduler/stack.go

@@ -300,6 +300,8 @@ func (s *SystemStack) SetJob(job *structs.Job) {
 	s.distinctPropertyConstraint.SetJob(job)
 	s.binPack.SetJob(job)
 	s.ctx.Eligibility().SetJob(job)
+	s.taskGroupCSIVolumes.SetNamespace(job.Namespace)
+	s.taskGroupCSIVolumes.SetJobID(job.ID)
 
 	if contextual, ok := s.quota.(ContextualIterator); ok {
 		contextual.SetJob(job)