wait with reboot for the finish of configuration update by local chef-client

Before the node is rebooted for reinstallation or after de-allocation, we need to wait for local chef-client to write pxe/dhcp config, so rebooted nodes can correctly pxe-boot.

https://bugzilla.novell.com/show_bug.cgi?id=844681

(backport of https://github.com/crowbar/barclamp-crowbar/pull/795)