update for new centos base images

updated for easier builds

library/centos

@@ -1,5 +1,6 @@
 # maintainer: The CentOS Project <[email protected]> (@CentOS)
 
-latest: git://github.com/CentOS/sig-cloud-instance-images@d4b27e196f2d150e9df062a1b962132f8216de23 docker
-centos7: git://github.com/CentOS/sig-cloud-instance-images@d4b27e196f2d150e9df062a1b962132f8216de23 docker
-centos6: git://github.com/CentOS/sig-cloud-instance-images@28b62101dd625dde14c8e6b8f5abf48b0329db69 docker
+latest: git://github.com/CentOS/sig-cloud-instance-images@f7732ef53029d6adfbadb7069c6666528e5c6d0e docker
+centos7: git://github.com/CentOS/sig-cloud-instance-images@f7732ef53029d6adfbadb7069c6666528e5c6d0e docker
+centos6: git://github.com/CentOS/sig-cloud-instance-images@e1ea1c01abea5f402c650caf12049a711373b27a docker
+centos5: git://github.com/CentOS/sig-cloud-instance-images@2674f34937662c5d200f12777ffee4f6ea0778a1 docker