Prevent the PNF from sending P7 messages after sending a STOP.indication

Upon stopping the PNF, when sending the STOP.indication to the VNF, set pnf_p7->terminate to 1.

Add a check on the PNF P7 send functions to not send a message after pnf_p7->terminate is set

nfapi/oai_integration/nfapi_pnf.c

@@ -1801,6 +1801,9 @@ int nr_stop_request(nfapi_pnf_config_t *config, nfapi_pnf_phy_config_t *phy, nfa
                                          .header.phy_id = req->header.phy_id};
   nfapi_nr_stop_indication(config, &resp);
   has_sent_stop_ind = true;
+  // Upon sending the STOP.indication mark P7 PNF to terminate, to not send any further messages to the VNF
+  pnf_p7_t *pnf_p7 = (pnf_p7_t *)(p7_config_g);
+  pnf_p7->terminate = 1;
 #ifdef ENABLE_WLS
   wls_pnf_close(pnf_p5_init_and_receive_pthread);
 #endif