Create drop-in directories for .network config

Summary:
# Context #
For classic hosts, chef creates a `.link.d` link drop-in directory.
However, the logic for creating `.network.d` network drop-in directory is missing.

# Changes #
* Added logic to create `.network.d` network drop-in directory for `shard(0)`

Differential Revision: D61904224

fbshipit-source-id: d78a06706730bd0a68e12767c1d46d5ef0e80f67

cookbooks/fb_networkd/resources/default.rb

@@ -164,6 +164,17 @@ def validate_network_addresses(conf)
       notifies :run, "execute[networkctl reconfigure #{conf['name']}]"
     end
 
+    if node.in_shard?(0)
+      # Create dropin directory for network config file.
+      dropin_dir = conffile + '.d'
+      directory dropin_dir do
+        action :create
+        owner node.root_user
+        group node.root_group
+        mode '0755'
+      end
+    end
+
     # This file is actively managed and already exists on the host so remove it
     # from the "on_host" array.
     if on_host_networks.include?(conffile)