Readd enum constant "skip" (#574)

Signed-off-by: Dominic Schabel <dominic.schabel@bosch-si.com>

hawkbit-ddi-api/src/main/java/org/eclipse/hawkbit/ddi/json/model/DdiDeployment.java

@@ -64,10 +64,15 @@ public class DdiDeployment {
     }
 
     /**
-     * Handling type for the update action.
+     * The handling type for the update action.
      */
     public enum HandlingType {
 
+        /**
+         * Not necessary for the command.
+         */
+        SKIP("skip"),
+
         /**
          * Try to execute (local applications may intervene by SP control API).
          */