/usr/share/xen-tools/centos-6.d/90-make-fstab is in xen-tools 4.4-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/xen-tools/centos-6.d/../common/90-make-fstab
/usr/share/xen-tools/centos-6.d/../common/90-make-fstab