Emits a different hostname for each network the node is on

Emits a different hostname for each network the node is on

Populates /etc/hosts with an entry for each IP address the node
is on, which will be useful to migrate services configuration from
using IPs into using hostnames.

This is how the lines look like on a host which doesn't have all ports:

  172.16.2.6 overcloud-novacompute-0.localdomain overcloud-novacompute-0
  192.0.2.9 overcloud-novacompute-0-external
  172.16.2.6 overcloud-novacompute-0-internalapi
  172.16.1.6 overcloud-novacompute-0-storage
  192.0.2.9 overcloud-novacompute-0-storagemgmt
  172.16.0.4 overcloud-novacompute-0-tenant
  192.0.2.9 overcloud-novacompute-0-management

the network against which the default (or primary) name is resolved
can be configured (for computes) via ComputeHostnameResolveNetwork

Change-Id: Id480207c68e5d68967d67e2091cd081c17ab5dd7