network_manager: Ensure that systemd-networkd is ready

We have some instances where systemd-networkd takes longer than usual
to configure. Combined with a service that manipulates network settings,
this sometimes causes addresses and routes to be lost because
phosphor-networkd writes new configurations before the configs are even
loaded from the RWFS.

Change-Id: I3dac95a0d54840423c0b0197a123318954a2e56a
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/xyz.openbmc_project.Network.service.in b/xyz.openbmc_project.Network.service.in
index 20e1631..5b8ae01 100644
--- a/xyz.openbmc_project.Network.service.in
+++ b/xyz.openbmc_project.Network.service.in
@@ -1,6 +1,7 @@
 [Unit]
 Description=Phosphor Network Manager
 After=obmc-mapper.target
+After=systemd-networkd.service
 
 [Service]
 ExecStart=/usr/bin/env phosphor-network-manager