Revert "Switch back to CentOS 7.0 image"
Revert "Switch back to CentOS 7.0 image"

This reverts commit ccb142aed31ec78b46e75f6436bc4e60a3003b78.

A `yum update` causes CentOS to be upgraded to 7.1
anyways

lightster/box-packer,lightster/box-packer,lightster/box-packer