Refactor common modules.

common/nomad-worker.nix

@@ -0,0 +1,9 @@
+{ ... }:
+{
+  # Enable Nomad client to run workloads
+  # Includes: Nomad client, Docker plugin, host volumes, NFS mount dependencies
+  # Used by: c1, c2, c3, zippy (all nodes that run Nomad jobs)
+  imports = [
+    ./nomad.nix
+  ];
+}