experiments: memcached: Run mutilate --loadonly during warmup

experiments/memcached.shared.sh

@@ -27,6 +27,7 @@ start_mutilate() {
 
 warmup() {
     echo "Warming up Memcached..."
+    sudo -u $SSH_USER $MUTILATE --loadonly
     sudo -u $SSH_USER $MUTILATE --noload -c100 $MUTCLIENTS -t30 -u 0
 }