do not write ifcfg-lo when rendering syscfg

This bug was originally filed in Launchpad as [LP: #1673853](https://bugs.launchpad.net/cloud-init/+bug/1673853)

Launchpad details

affected_projects = []

assignee = None

assignee_name = None

date_closed = None

date_created = 2017-03-17T18:27:46.244318+00:00

date_fix_committed = None

date_fix_released = None

id = 1673853

importance = medium

is_complete = False

lp_url = https://bugs.launchpad.net/cloud-init/+bug/1673853

milestone = None

owner = smoser

owner_name = Scott Moser

private = False

status = confirmed

submitter = smoser

submitter_name = Scott Moser

tags = []

duplicates = []

_Launchpad user **Scott Moser(smoser)** wrote on 2017-03-17T18:27:46.244318+00:00_

As discussed some in merge proposal at [1].
The sysconfig renderer could use some work.

a.) seems like we should not be rendering ifcfg-lo at least in the case that it already exists.
b.) we should be able to now replace _write_network with something that uses eni.convert_eni_data
like http://paste.ubuntu.com/24196078/
--
[1] https://code.launchpad.net/~smoser/cloud-init/+git/cloud-init/+merge/319943