Move policy into a mixin

Author: JohnGarbutt

etc/kayobe/environments/baremetal-policy/README.rst

@@ -0,0 +1,15 @@
+Policy for a baremetaluser role 
+===============================
+
+When deploying Slurm on baremetal nodes,
+it is typical to select a specific baremetal node,
+and give it the expected hostname. We allow this
+via a tweak to Nova policy.
+
+Similarly, it is common that the IP address has
+to match the expected one for the given node.
+We tweak neutron policy to allow fixed IPs,
+even when we do not own the network.
+
+We should never use the admin role to do these
+operations, as it has far too much privilege.