We should not use http://mirror.centos.org/centos/7/atomic/x86_64/adb/ as it is not not maintained, the workaround will be to use a COPR repo or the new Minishift repo in CentOS PaaS SIG (when it is ready).
[1] https://github.com/minishift/minishift-centos-iso/pull/108/files
[2] https://copr.fedoraproject.org/