netdev_pformat does not show unconfigured devices

The changes in commit 6d48d265a05 made netdevinfo.netdev_pformat() stop
showing information about network devices that do not have an address.

see below:

$ git checkout --quiet 6d48d265a05^
$ git rev-parse HEAD
4c573d0e0173d2b1e99a383c54a0a6c957aa1cbb
$ python3 -c 'from cloudinit import netinfo; print(netinfo.netdev_pformat())'
+++++++++++++++++++++++++++Net device info++++++++++++++++++++++++++++
+--------+-------+-----------+-----------+-------+-------------------+
| Device | Up | Address | Mask | Scope | Hw-Address |
+--------+-------+-----------+-----------+-------+-------------------+
| eth0: | False | . | . | . | 00:16:3e:de:51:a6 |
| lo: | True | 127.0.0.1 | 255.0.0.0 | . | . |
| lo: | True | . | . | d | . |
+--------+-------+-----------+-----------+-------+-------------------+
$ git checkout --quiet master master
error: pathspec 'master' did not match any file(s) known to git.
$ git checkout --quiet master
$ git rev-parse HEAD
4ed164592fe8cb15758cacf3cb3f8c7d5ab7c82e
$ python3 -c 'from cloudinit import netinfo; print(netinfo.netdev_pformat())'
+++++++++++++++++++++++Net device info++++++++++++++++++++++++
+--------+------+-----------+-----------+-------+------------+
| Device | Up | Address | Mask | Scope | Hw-Address |
+--------+------+-----------+-----------+-------+------------+
| lo | True | 127.0.0.1 | 255.0.0.0 | host | . |
| lo | True | ::1/128 | . | host | . |
+--------+------+-----------+-----------+-------+------------+

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: cloud-init 18.2-14-g6d48d265-0ubuntu1 [modified: usr/lib/python3/dist-packages/cloudinit/netinfo.py]
ProcVersionSignature: Ubuntu 4.15.0-13.14-generic 4.15.10
Uname: Linux 4.15.0-13-generic x86_64
ApportVersion: 2.20.9-0ubuntu5
Architecture: amd64
CloudName: LXD
Date: Mon Apr 23 16:39:48 2018
PackageArchitecture: all
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 LANG=C.UTF-8
SourcePackage: cloud-init
UpgradeStatus: No upgrade log present (probably fresh install)
user_data.txt:
 #cloud-config
 {}