centos 6.5 is deprecated on the mirror sites

[Jerry Zhao]

http://mirror.centos.org/centos/6.5/readme

and it is breaking CI.

2015-01-06 18:25:36.359 | ++ curl -f -L -o /tmp/openssh-5.3p1-94.el6.x86_64.rpm.tmp http://mirrors.hustunique.com/centos/6.5/os/x86_64/Packages/openssh-5.3p1-94.el6.x86_64.rpm
2015-01-06 18:25:36.732 | % Total % Received % Xferd Average Speed Time Time Time Current
2015-01-06 18:25:36.733 | Dload Upload Total Spent Left Speed
2015-01-06 18:25:37.551 |
  0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0
154 154 154 154 0 0 210 0 --:--:-- --:--:-- --:--:-- 397
  0 154 0 0 0 0 0 0 --:--:-- 0:00:01 --:--:-- 0
2015-01-06 18:25:37.552 | curl: (22) The requested URL returned error: 404 Not Found
2015-01-06 18:25:37.553 | ++ [[ 22 != \0 ]]
2015-01-06 18:25:37.553 | ++ echo 'failed to download openssh-5.3p1-94.el6.x86_64.rpm'
2015-01-06 18:25:37.553 | failed to download openssh-5.3p1-94.el6.x86_64.rpm

It is time to switch to a newer centos release

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: dev/experimental
Review: https://review.openstack.org/145406

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: dev/experimental
Review: https://review.openstack.org/145476

[OpenStack Infra (hudson-openstack)]

Change abandoned by Jerry Zhao (<email address hidden>) on branch: dev/experimental
Review: https://review.openstack.org/145476
Reason: superseded by xiaodong's change

[OpenStack Infra (hudson-openstack)]

Change abandoned by Jerry Zhao (<email address hidden>) on branch: dev/experimental
Review: https://review.openstack.org/145406
Reason: superseded by xiaodong's change