OpenVZ containers (virtual machines) don't have an /etc/fstab file because the partitioning is controlled from the host system. To set noatime for a VM, you can run
Code:
vzctl set veid --noatime yes --save

on the host system and restart the VM (replace veid with the ID of the container; for example, if the container has the ID 101, run
Code:
vzctl set 101 --noatime yes --save

and restart the container:
Code:
vzctl restart 101