Make baremetal directory setup baremetal specific.

Per 1183532 we don't need the tftp directory touched or altered on
non-baremetal compute nodes.

Change-Id: I6e9912fa08e0a57fce4d24222a9691aeb1cb2fc2
Fix permission errors with nova-kvm.

Per bug 1183274 qemu needs read permission on the instance files and
backing files or else it cannot open (and then chown/chmod) them.

At the same time I removed a little cruft that had built up - we don't
use /var/run/nova/instances at all.

Change-Id: Idf77a65269c0e238097a4d2cb6932c30e0e031c5
Merge "Make baremetal directory setup baremetal specific."
Merge "Fix permission errors with nova-kvm."