runscript: use the previously defined "user"

There is already a logic set earlier in the code to define "user" if --user is passed as parameter, and default to the user with the lowest ID no none is provided.
This patch uses this "user" to run the job instead of always applying the default.

netbox/extras/management/commands/runscript.py

@@ -125,7 +125,7 @@ class Command(BaseCommand):
         job = Job.objects.create(
             object=module,
             name=script.class_name,
-            user=User.objects.filter(is_superuser=True).order_by('pk')[0],
+            user=user,
             job_id=uuid.uuid4()
         )