ANSUPDATE-25 Cleanup Ironic Reservations on undercloud

Ironic can end up in a state where nodes are locked and are unable to
rebuild due to the presence of the lock.  We will now clear any locks
that we find upon restart of the undercloud.

Ironic Bug: https://bugs.launchpad.net/ironic/+bug/1382698

Change-Id: Iafff3c42d34b419d8f66cec4fc8ba99c88d12530