Add support to DataSourceOVF for configuring network interfaces

This bug was originally filed in Launchpad as [LP: #1247055](https://bugs.launchpad.net/cloud-init/+bug/1247055)

Launchpad details

affected_projects = []

assignee = None

assignee_name = None

date_closed = None

date_created = 2013-11-01T10:53:16.810549+00:00

date_fix_committed = None

date_fix_released = None

id = 1247055

importance = medium

is_complete = False

lp_url = https://bugs.launchpad.net/cloud-init/+bug/1247055

milestone = None

owner = dave-johnston

owner_name = Dave Johnston

private = False

status = triaged

submitter = dave-johnston

submitter_name = Dave Johnston

tags = []

duplicates = []

_Launchpad user **Dave Johnston(dave-johnston)** wrote on 2013-11-01T10:53:16.810549+00:00_

Some of the datasources such as NoCloud offer the ability to configure network interfaces via meta-data.
It would be useful if the OVFDataSource could provide a similar feature, using OVF properties.

The OVF environment doesn't lend itself to writing a multi-line document i.e

network-interfaces: |
  iface eth0 inet static
  address 192.168.1.10
  network 192.168.1.0
  netmask 255.255.255.0
  broadcast 192.168.1.255
  gateway 192.168.1.254
  dns-nameservers 10.20.10.110 10.20.10.113
  dns-search myopwvbfs.com

Instead, indvidual properties should be used to make up the network settings, which could then be translated to the multi-line format internally.