Rackspace no longer specifies CentOS point releases in their base image
names. This means no more CentOS 6.5 PVHVM image instead we have a
CentOS 6 PVHVM image. Go ahead and use the new non point release
specific image in nodepool to accomodate this change.
Change-Id: I3f9423722615fbacf5ee53a02987fc2052491ef5