Add systemd-networkd back into the mix.

systemd-networkd was removed because NetworkManager was chosen as the de-facto
networking configuration implementation as discussed in
coreos/fedora-coreos-tracker#24 but removing it entirely
restricts end user choices to fit their use cases.

Since systemd-networkd can live along side of NetworkManager this PR adds it back in.

manifests/fedora-coreos-base.yaml

@@ -44,16 +44,6 @@ remove-from-packages:
   # We're not using resolved yet.
   - [systemd, /usr/lib/systemd/systemd-resolved,
               /usr/lib/systemd/system/systemd-resolved.service]
-  # We're not using networkd.
-  - [systemd, /etc/systemd/networkd.conf,
-              /usr/lib/systemd/systemd-networkd,
-              /usr/lib/systemd/systemd-networkd-wait-online,
-              /usr/lib/systemd/network/.*,
-              /usr/lib/systemd/system/systemd-networkd.service,
-              /usr/lib/systemd/system/systemd-networkd.socket,
-              /usr/lib/systemd/system/systemd-networkd-wait-online.service]
-  - [systemd-container, /usr/lib/systemd/network/.*]
-
 
 remove-files:
   # We don't ship man(1) or info(1)