Use relative name for class inclusion

This patch replces the remaining usage of absolute name in 'require',
and makes all class inclusion depend on relative name.

Change-Id: Idde492675c2eedaa30a418b104603450319b92b8

manifests/controller.pp

@@ -90,9 +90,9 @@ class ovn::controller(
   }
 
   if $enable_dpdk {
-    require ::vswitch::dpdk
+    require vswitch::dpdk
   } else {
-    require ::vswitch::ovs
+    require vswitch::ovs
   }
 
   include stdlib