Set PNF slot_ahead to 1 when using WLS as the transport mechanism

nfapi/oai_integration/nfapi_pnf.c

@@ -2339,7 +2339,11 @@ void handle_nr_slot_ind(uint16_t sfn, uint16_t slot)
     //send VNF slot indication, which is aligned with TX thread, so that it can call the scheduler
     //we give four additional slots (2ms) which should be enough time for the VNF to
     //answer
+#ifndef ENABLE_WLS
   int slot_ahead = 2 << mu;
+#else
+  int slot_ahead = 1;
+#endif
   uint16_t sfn_tx = sfn;
   uint16_t slot_tx = slot;
   sfnslot_add_slot(mu, &sfn_tx, &slot_tx, slot_ahead); // modify: do in place