fix repo update issue

library/centos

@@ -7,8 +7,8 @@ centos7: git://github.com/CentOS/sig-cloud-instance-images@0ab04b50ac631d1371a22
 7: git://github.com/CentOS/sig-cloud-instance-images@0ab04b50ac631d1371a2241171f19655c2870020 docker
 
 # CentOS 6 rolling builds
-centos6: git://github.com/CentOS/sig-cloud-instance-images@3d48b279af1a995f021578a056262ffd1ff233f3 docker
-6: git://github.com/CentOS/sig-cloud-instance-images@3d48b279af1a995f021578a056262ffd1ff233f3 docker
+centos6: git://github.com/CentOS/sig-cloud-instance-images@c2f6c5329d41005d5f9f14274e2f490098ec9b21 docker
+6: git://github.com/CentOS/sig-cloud-instance-images@c2f6c5329d41005d5f9f14274e2f490098ec9b21 docker
 
 # CentOS 5 rolling builds
 centos5: git://github.com/CentOS/sig-cloud-instance-images@4bf8330498e1c10cf365aff31d2a8a5c3254c2cf docker