F1: force low ULSCH max frame inactivity to have more reliable ping test

ci-scripts/conf_files/gNB_SA_DU.conf

@@ -177,6 +177,7 @@ MACRLCs = (
     remote_n_portd  = 2152;
     pusch_TargetSNRx10          = 200;
     pucch_TargetSNRx10          = 200;
+    ulsch_max_frame_inactivity = 1;
   }
 );