Django1.7: Renamed get_query_set to get_queryset in {AL,NS}_NodeManager

Avoids the below warnings on Django1.7

RemovedInDjango18Warning: `AL_NodeManager.get_
query_set` method should be renamed `get_queryset`.

RemovedInDjango18Warning: `NS_NodeManager.get
_query_set` method should be renamed `get_queryset`.