[LibOS] Use 'ab -k' in benchmark-http.sh

LibOS/shim/test/apps/lighttpd/benchmark-http.sh

@@ -11,6 +11,7 @@ DOWNLOAD_HOST=$1
 DOWNLOAD_FILE=random/10K.1.html
 REQUESTS=10000
 CONCURRENCY_LIST="1 2 4 8 16 32 64 128 256"
+OPTIONS="-k"
 RESULT=result-$(date +%y%m%d-%H%M%S)
 
 touch $RESULT
@@ -21,8 +22,8 @@ do
 	for CONCURRENCY in $CONCURRENCY_LIST
 	do
 		rm -f OUTPUT
-		echo "ab -n $REQUESTS -c $CONCURRENCY http://$DOWNLOAD_HOST/$DOWNLOAD_FILE"
+		echo "ab $OPTIONS -n $REQUESTS -c $CONCURRENCY http://$DOWNLOAD_HOST/$DOWNLOAD_FILE"
-		ab -n $REQUESTS -c $CONCURRENCY http://$DOWNLOAD_HOST/$DOWNLOAD_FILE > OUTPUT || exit $?
+		ab $OPTIONS -n $REQUESTS -c $CONCURRENCY http://$DOWNLOAD_HOST/$DOWNLOAD_FILE > OUTPUT || exit $?
 
 		sleep 5