Use ansible instead of direct ssh calls

Instead of a shell script looping over ssh calls, use a simple
ansible playbook. The benefit this gets is that we can then also
script ad-hoc admin tasks either via playbooks or on the command
line. We can also then get rid of the almost entirely unused
salt infrastructure.

Change-Id: I53112bd1f61d94c0521a32016c8a47c8cf9e50f7