Add swap to enter point to dolphinscheduler AMI

[zhongjiajie]

currently, our add SWAP seem not work

packer_tmpl/aws/ami/dolphinscheduler/scripts/dolphinscheduler_builder.sh

Lines 50 to 55 in e11dc26

	# Add swap mount point, default memory is 4G
	sudo dd if=/dev/zero of=/swapfile bs=128M count=32
	sudo chmod 600 /swapfile
	sudo mkswap /swapfile
	sudo swapon /swapfile
	sed -i -e '$a/swapfile swap swap defaults 0 0' /etc/fstab

we should find some way to make it work