tunings: Set busy_poll to 16384 for less artifact

When we limit the QPS, a busy_poll value produces latency artifacts at low throughput.

tunings/kernel_polling.sh

@@ -3,6 +3,6 @@ if [ ! "$(uname -r)" == "5.15.79-peter" ]; then
     exit 1
 fi
 
-sysctl net.core.busy_poll=128
+sysctl net.core.busy_poll=16384
 # NAPI locality is needed for multi-threaded experiments
 NAPI_LOCALITY=true