Add init_xxx_node.sh

This script sets the hostname and configures networking in the node VM.
It gets the hostname from its own file name (which is appropriately set
by vm_build_node when copying the file).

Partial-Bug: 1312764
Implements: blueprint openstack-training-labs
Change-Id: I9d0daad40462202c42ddd3a591f93b23d9512d53
Merge "Add init_xxx_node.sh"