create-nodes: allow multiple bridge names
create-nodes: allow multiple bridge names

This patch updates create-nodes so that it supports
configuring VMs which are attached to multiple baremetal
bridges. The name of the virtual machine (previously based
on the bridge) has been adjusted to concatonate all the
bridge names as a convention when naming virtual machines
with multiple bridges.

Change-Id: I5857629df7c8f7bc00c3a475a3e8ffc6f7e99c93

rdo-management/tripleo,rdo-management/tripleo