AssignPnfBB - set orchestration status to Assigned after successful assignment

CoS:

• AssignPnfBB should set PNF orchestration status to Assigned
  • Status should be switched after PNF was successfully created in AAI and assigned to service instance

How to demo:

• Run demo flow containing AssignPnfBB on some demo service model (use SO official REST API to start instantiation)
• Show in SO Monitoring that flow with AssignPnfBB has been executed
• Show that entry for PNF was created in AAI with requested pnfCorrelationId (PNF instance name). 
• Show that PNF orchestration status was set to Assigned

Arch details:

• Status change should be implemented similarly as in AssignVnfBB (see "AAI Update (vnf)" at the end of BPMN)
  • Add separate task at the end of AssignPnfBB 
  • Similarly as for VNF implement methods:
    • AAIUpdateTasks.updateOrchestrationStatusAssignedPnf()
    • AAIPnfResources.updateOrchestrationStatusPnf()