Delete node while waiting for deploy

During a deployment, some drivers set the node.provision_state to DEPLOYWAIT
-- eg, while waiting for a callback from the deploy ramdisk agent. This
change makes it possible to de-provision the node during this window (ie,
clean up the files and network env, and power it off).

Note that this state is explicitly included in the check within the
ConductorManager's do_node_tear_down; it was the API check that prevented
this.

Also modified a user message to indicate that the node is being
provisioned or decommissioned.

Change-Id: Ia67ec635c36f643d99795d91f9dfb10b577f033f
Closes-Bug: #1291056
Merge "Delete node while waiting for deploy"